You bring up the biggest problem with martial arts history. Not only is it all based on folktale, no one is really going to invest that serious an effort in martial archeology at this time because it's a lot of hard work. Just look at what a horrid state Chinese hopology is in, and you know that the quest for other Shaolin temples is pretty low priority.
That being said, here's my Shaolin koan about this:
How many Shaolin Temples are there in the USA right now?
Answer this, and it doesn't take much to generalize our current situation to what may have occured in the past.

Gene Ching
Asst. Publisher
Kungfu Qigong Magazine & www.KUNGFUmagazine.com