I'm an RT as well and for the last week of my research yes so far Excelsior is the only online program but some local community colleges are offering the RT to RN in the classroom setting 1 year program.
If it helps you any, Rue and the College Network absolutely do not have to go hand in hand with Excelsior. I've never heard of any other program that will transition RT to RN, at least not online.
Excelsior can be quite difficult, but it can be done rather quickly. My husband (who did paramedic to RN) did like a lot of people in that he was enrolled for several months without completing anything. Unlike a lot of people though, once he figured out that he just had to schedule the tests and that would motivate him to study for them. He was done in less than 1 year from the time he actually started taking tests.