I've got 25.40 and we currently have 9 T-1s. Even though I don't have another T-1 card I just built a 10th T-1 card and then deleted it to test this scenario for you. So to answer your question, I say you can have more than 10.
However, we do have 4 cabinets all with IP connectivity and survivablity. The T-1s are also spread out through all 4 cabinets.
Hope this helps you out.