When an egg hatches, is every pokemon in the pool as likely to come out of it?

While Niantic has not confirmed anything there's a theory that the location of the egg of which it was acquired influences the outcome. By that I'm assuming that the GPS location of the pokestop is stored and then used to find which pool of mons are appropriate.

It makes sense when you think about it. Pokemons that are common to spawn near certain pokestops are more likely to appear near them when luring.

I had a theory myself that your location when the egg hatches influences the pool of pokemons that you can get but I don't hava data to support that theory.

There are no facts out there though, only theories. I'm leaning towards the theory I linked until proven otherwise. I just found it and I'm going to keep an eye on it.