The presence of archivists in a setting allows a wyrm wizard's spell research to yield true creation…
If the setting features no archivists then I agree with this fine answer that the wyrm wizard is sunk. The 8th-level creation domain spell true creation [conj] (Spell Compendium 224) otherwise only appears on the list for the domain creation (272). While individuals may have somehow added to their spell lists the true creation spell, so far as I'm aware, no base or prestige class has a spell list that includes the true creation spell.
If there are archivists in the setting then here's how this works. For completeness, every even level the prestige class wyrm wizard gains the extraordinary ability spell research that, in part, says
[S]elect one spell from any class's spell list (including divine spells), of a level equal to or lower than the highest-level arcane spell you can prepare and cast. You can add this spell to your arcane spellcasting class spell list as a spell of the same level…. (Dragon Magic 55)
At level 1 the base class archivist gains the (presumably natural) ability prayerbook that, in part, says
[A]n archivist can also add spells found on scrolls containing divine spells to his prayerbook, but he must make any rolls and spend the time required (see Adding Spells to a Wizard’s Spellbook on page 178 of the Player’s Handbook). The archivist can learn and thus prepare nonclerical divine spells in this fashion…. (Heroes of Horror 83)
In other words, an archivist who acquires a divine scroll of true creation (up to 1,000 gp gp) (CL 15) (5,500 gp; 0 lbs.) can use that scroll to add the true creation spell to his prayerbook. However, it's not the Player's Handbook but the Rules Compendium that provides the crucial information about magical writings that applies to the question. Copied Spells, in part, says
Spellcasters who use spellbooks [and, by extension, prayerbooks] can add a spell to their book whenever they find one on a scroll or in another caster’s spellbook. The spell to be copied must be on the copier’s class spell list. (160)
Thus an archivist must have the true creation spell on his spell list. If an archivist didn't have the true creation spell on his spell list, then the archivist wouldn't be able to add the true creation spell to his prayerbook using a divine scroll of true creation.
(If you're not using the Rules Compendium, this process is much less clear—see here. Also, this makes the archivist's spell list absurdly long, a lament shared here and here, for instance. Finally, this means that an archivist might not know the extent of his own spell list. This last may initially seem strange, but that happens even if using just the core rules: Successfully Researching Original Spells (Dungeon Master's Guide 198 and here and not be confused with the wyrm wizard ability) already seems to add new spells to a class's spell list—not just an individual's spell list—, totally without the class's members' knowledge. Hilarious trolling may ensue.)
To sum, a wyrm wizard who gains an iteration of the spell research ability when he's also capable of casting 8th-level spells can, by plumbing the archivist's ridiculously expansive spell list, add the true creation spell to that wyrm wizard's own unique spell list.
…But a wyrm wizard's spell research adds the spell only to that wyrm wizard's spell list
The 8th-level Sor/Wiz spell shades [conj] (PH 276), in part, says, "This spell functions like shadow conjuration, except that it mimics sorcerer and wizard conjuration spells of 8th level or lower." The 4th-level Sor/Wiz spell shadow conjuration [conj] (ibid.) adds little to this, saying, "Shadow conjuration can mimic any sorcerer or wizard conjuration (summoning) or conjuration (creation) spell of 3rd level or lower." Here are two trains:
- "All Aboard!": The shadow conjuration spell et al. don't say anything about spell lists. If a particular sorcerer or wizard adds a spell to his sorcerer or wizard spell list, then that spell is now a sorcerer or wizard spell—even if it's just a sorcerer or wizard spell for that individual sorcerer or wizard. This makes any sorcerer or wizard spell added to an individual sorcerer or wizard's spell list eligible to be mimicked with that particular sorcerer's or wizard's shadow conjuration spell et al.
- "Everbody Off!" Because "any sorcerer or wizard conjuration… spell" and the like means that the spell must actually be on the sorcerer or wizard spell list, and the true creation spell isn't added to every sorcerer or wizard spell list by any officially available source, it's never on the sorcerer spell list or the wizard spell list even if it's on your sorcerer or wizard spell list. Thus, as per this fine answer, it can't be mimicked with the shades spell.
Ask the DM which train he prefers.
Sidebar: So you've added true creation to your own spell list
If the true creation spell is on a certain specific sorcerer's or wizard's sorcerer or wizard spell list—like yours, for instance, through a wyrm wizard's spell research ability—, then you can cast the true creation spell, you can activate magic items as if the true creation spell were on your appropriate spell list (because it is), and you can trigger the true creation spell so as to create magic items that have the spell as a prerequisite for their creation—and if one of those magic items is a scroll, it'll even be an arcane scroll of true creation.
However, the vast majority of wizards can't copy the true creation spell from your spellbook into their spellbooks (according to the Rules Compendium anyway). Sorcerers and wizards generally won't be able to activate magic items you create with the spell trigger activation method if the true creation spell must be found on their spell lists. And sorcerers and wizards must make Use Magic Device skill checks to employ that scroll. (One of the requirements scroll activation is that the "user must have the spell on his or her class list" (DMG 238).)
Note: Personally, I think that "All Aboard!" is more persuasive but that "Everybody Off!" makes for a more balanced game.