I've used RTD bike racks many times before. For a while, I was using them every day when I commuted from Denver into Broomfield. They are very secure, the bike isn't going anywhere. Once I put the bike in, I give it a good wiggle, and it will be pretty obvious is the rack is broken.

I would also not lock the bike to the rack. It delays the bus. Just throw it on and go.

I like to sit at the front of the bus to watch the bike. If someone looked like they were stealing it, you could easily jump off and deal with it.