One designer says No
The Dragon #298 Sage Advice column "Official Answers to Your Questions" includes this exchange:
Question: Is it possible for wizards to cast curative spells? For example, cure moderate wounds or cure light wounds? It seems that they can under the right circumstances. Suppose Willie, a halfling bard in my party, has the Scribe Scroll feat. The Player's Handbook says wizards, sorcerers, and bards all cast arcane magic. That means the cure spells a bard casts are arcane and not divine regardless of what the spell is, right? That also means that if Willie scribes a scroll with cure light wounds on it, the scroll will still be an arcane scroll. If that's correct, it means that if my wizard gets the cure light wounds scroll from Willie, he can scribe it into his spell book and then prepare it as an arcane spell that he can use time and time again, right?
Answer: You can't read a spell off a scroll unless the spell is on your class list (see page 203 in the Dungeon Master's Guide). You also cannot scribe a spell into your book unless its [sic] on your class list. Only another bard can use Willie's cure light wounds scrolls (because bards are the only arcane casters who have cure spells on their class lists).
Remember that spell trigger items, such as wands, do not come in arcane or divine versions. If a bard makes a wand of cure light wounds, any character who has cure light wounds on his spell list can use the wand. (112)
This ruling predates the Dungeons and Dragons 3.5 revision, but as the topic's remained unmentioned since then (so far as I could determine, anyway), this ruling should be applicable to any 3.5 campaign with minor revisions by the DM (DMG (2003) 4). Although then-Sage Skip Williams's Rules of the Game columns should be read with salt shaker in hand, he's still one of the three primary designers of Dungeons and Dragons, Third Edition, giving this ruling at least some credibility. (By the way, at the time, Dragon was still published by Wizards of the Coast, not Paizo, if that makes a difference in determining if something's authoritative enough for your group.)
By the book, though, a wizard can possibly transcribe an off-list spell from a scroll into his spellbook...
A wizard that acquires an arcane scroll of cure light wounds [conj] (PH 215-6) (1st-level spell at caster level 2) (DMG 239) (50 gp; 0 lbs.) or even a divine scroll of cure light wounds [conj] (PH 216-7) (1st-level spell at caster level 1) (DMG 241) (25 gp; 0 lbs.) must follow these steps to get it into his spellbook:
- The wizard must decipher the magical writing on the scroll of cure light wounds by either making a Spellcraft skill check (DC 21) or employing the 0-level Sor/Wiz spell read magic [div] (PH 269).
- The wizard must understand the spell cure light wounds by taking 1 day and making a Spellcraft skill check (DC 16). Note: Some restrictions apply.
- The wizard must copy the spell cure light wounds into his spellbook by taking 1 day, spending 100 gp, and having the spell occupy 1 page of his spellbook.
For this to work, the DM must rule that the wizard is not activating the spell (which is what happens when the spell on the scroll is cast)—the wizard can't do that because to activate the spell on the scroll both the "spell must be of the correct type" and a wizard "must have the spell on his or her class list" (DMG 239).
Instead, the DM must rule that using the scroll to add the spell to his spellbook is a different process that doesn't so much as activate the spell but, like, readies the spell for transcription or something. Nonetheless, when this this different process is used, "a spell successfully copied from a magic scroll disappears from the parchment" (179). Such a ruling isn't, in itself, a huge leap for the DM to make, but it's not an inconsequential one either, so a player asking the DM about such a distinction should make clear his reason for asking.
...And a wizard can prepare a spell that's in his spellbook...
The Player's Handbook on Spell Preparation Time says, "After resting, a wizard must study her spellbook to prepare any spells that day" (178). That is, if a spell's in the wizard's personal spellbook, the spell's already gone through the process above (or a similar process that's led to the spell being in the wizard's spellbook). Nothing prevents the preparation of any spell in the wizard's spellbook—even if the spell's source is weird or its typical list alien.
...But a wizard can't usually cast an off-list spell
The wizard class feature spells says, "A wizard casts arcane spells... which are drawn from the sorcerer/wizard spell list" (PH 56). While the text doesn't say a wizard can't cast spells from lists other than the sorcerer/wizard spell list, the game usually uses inclusive language (explaining what can be done), saving for confusing corner cases exclusive language (explaining what can't be done). That is, just because the text doesn't say the wizard can't doesn't mean the wizard can, for example, turn his foes into lawn furniture (at least until the wizard can cast polymorph any object, anyway).
Hence, with a generous DM, a wizard can understand and copy from a scroll any spell into his spellbook, and a wizard can even prepare that spell if he has a spell slot of the appropriate level, but the wizard can't cast the spell unless it's on the sorcerer/wizard spell list.
Again, with a generous DM, it's possible that such prepared-but-uncastable spells could still be used, for example, during item creation; that is, the item creation process often "triggers" spells—the prepared spell's expended as if the spell were cast but the spell's not actually cast. So using that generous DM's rulings, such a wizard could, for example, create—but, oddly, still not normally use—a wand of cure light wounds.
Also, when a wizard that has added to his spellbook the spell cure light wounds from a divine scroll of cure light wounds then creates his own scroll of cure light wounds, the DM must decide whether the resultant cure light wounds spell on that scroll is arcane or divine, because, honestly, I have no idea, and, really, if you've such a generous DM that you've gotten this far, why are you trying to make his head explode? Neither could that wizard normally use that (arcane? divine?) scroll of cure light wounds. Seriously, do that nice DM a solid and just brew a darn potion.
Of course, none of this precludes a wizard from employing in whatever capacity off-list spells that that specific wizard has somehow uniquely added to his wizard's spell list. In that case, the spells aren't off-list anymore, so it doesn't matter.