All intelligent items have the ability to at least communicate empathically with their owner. Source, see Senses and Communication.
What makes someone an item's owner?
I can see a few candidates:
The rules for intelligent magic items use "owner" and "possessor" somewhat interchangeably. And, of course, in general the owner of a magic item is presumed to be the possessor. Magic items with high Egos are said to be able to take over their owners in one place, and in another place the rules for when such an item can dominate its possessor are detailed:
Intelligent items with high Ego scores are difficult to control and can sometimes take control of their owner, making them dangerous to possess.
[…]
When an item has an Ego of its own, it has a will of its own. The item is absolutely true to its alignment. If the character who possesses the item is not true to that alignment’s goals or the item’s special purpose, personality conflict—item against character—results. Similarly, any item with an Ego score of 20 or higher always considers itself superior to any character, and a personality conflict results if the possessor does not always agree with the item.
When a personality conflict occurs, the possessor must make a Will saving throw (DC = item’s Ego). If the possessor succeeds, she is dominant. If she fails, the item is dominant. Dominance lasts for 1 day or until a critical situation occurs (such as a major battle, a serious threat to either the item or the character, and so on). Should an item gain dominance, it resists the character’s desires and demands concessions […]
So the rules already lay out a way for an intelligent magic item to work for other aims (possibly including further the agenda of its creator or another party) against its possessor's aims, even if its possessor is its owner, and make no distinction between the item's current owner and any "true" owner it might claim to have.
What's more, there are some interesting rules quirks that would arise if the owner could be anyone besides the possessor. In particular, the ability to pull an NPC that might be hundreds of miles away into initiative is certainly quite impressive.
Possession does not need to be limited to touch, either; Paizo's blog added a specific intelligent magic item ability, Leaping:
As long as the possessor has the item on his person, as a free action he can call out to the item, causing it to jump into his hand (if that is how it is wielded) or equip itself in the appropriate slot (if it takes up a slot).
I don't think there are any rules for that.
Personally I'd handle it like this: There are three kinds of "intelligent" items.
1: The intelligence is the result of something being trapped in the item.
For example a powerful demon is trapped in the (now corrupted) holy sword that once killed him. His owner will always be whoever he deems most likely to release him.
2: The item is intelligent, but has no agenda and/or sway over the items powers. Its purpose is purely advising its user. So the owner is simply whoever manages to claim it.
3: True intelligence. The item has not only intelligence, but also an agenda and personality.
In this case I generally agree with Dale M: The owner is whoever is deemed worthy by the item.
Two very simple reasons:
1: If the item is TRULY intelligent its creator was exceedingly powerful. It is reasonably to assume that it has safeguards against being misused against its creators will. After all that guy DID invest a lot of time and effort making this.
2: Occams razor. If the intelligence of the item does nothing meaningful, there is no reason to have it in the first place.
Of course, as always, option number 3 opens up a lot of adventure possibilities. After all, there is no rule(ing) without exception.
Maybe the absurdly powerful lich Nagash the Grumpy (also known as "he who must not be smiled at") has gotten hold of a divine artifact, and has begun an epic ritual to bend it to his will?
PS: This is purely along the lines of character-item interaction.
The legal owner of the item is of course decided however the game world handles such things.
And what the item can actually do if in the hands of somebody it deems inappropriate is, naturally, up to the DM. As i just said in a comment: Remember that one ring?
In most legal traditions an item is owned by the person who created it and to those whom it was lawfully transferred. So, you have to go back through all the legal transfers of the item back to the original creator: fortunately you have an eyewitness to all of these, the item itself - it can tell you who owns it. Alternatively, you may live in a kingdom with a central authoritative register of magic items.
Of course, if you happen to live in a kingdom where slavery is illegal, the item owns itself.
Almost certainly, the PCs are not the owner because they likely stole the item - probably with violence from someone who may or may not have been the true owner.
Intelligent magic items are ... intelligent NPCs. They have the capacity, subject to being dominated by their possessor, of deciding who their owner is. For example, the One Ring was only ever owned by Sauron irrespective of who happened to possess it.
You can if you wish, broaden the definition of "owner" to include "possessor" which is what I think you are thinking of by the examples in your question. You can even apply the aphorism that Possession is nine-tenths of the law, which basically means that the person who has something is presumed to own it unless someone else can prove that they own it.
However, in the context of the rules - an item that can speak can be heard by anyone within earshot, owner or no. It would make sense that telepathy works the same way up to whatever range seems sensible including (none is given) - anywhere from touch to everywhere. Empathy likewise.
