I assume you mean Swatara State Park.
Yes, there are a number of mountain bike trails there built specifically for the bikers.
My friends go there a lot.
I know they are close to the AT but I don't know that any are actually on it.
We had heard, and saw signs in Bosnia and Montenegro that the hiking trail we were on was also a mountain bike trail.
No way, could someone bike much of that trail as it was a lot of rocks and rough trail.