Actually, I also doubt that there are terrorist training camps just outside Islamabad. Maybe safe houses or something like that, but there is no way the Pakis would not have found and taken action against a terrorist training facility right next to their capital city and biggest military bases.
There are camps all over Pakistan that the Pakistan military uses to train terrorist that they send to Kashmir. This one was probably sublet for Al Qaeda. Pakistan is in reality one big terrorist camp of a country.