The IVs of a traded Pokemon are whatever IVs the Pokemon had when the player who originally owned it caught it.
So if I had a Keldeo, for example, and it had 15 IVs in each stat. If I traded it to someone those IVs would stay the same.
So they can be perfect and they can be all the same (all depends on luck). They are randomly generated when the Pokemon was first encountered by the original trainer, but will not change when traded.