Sure! He can find it in AD (or it can find him by showing up on his pillow/thumping him on the head) courtesy of the Animus. As they said, working is a bit of a specific term, so he'll find that he can't just annihilate whoever he pleases with a single blast/flatten a portion of the city, but other than those little things, should work find with permissions post and everything.

And of course, his taking up and using the spectre will be the equivalent of his signing a contract with the Animus, so to speak~ Nothing specific now, but he may find himself subject to their manipulations should a player plot ever call for it >3