I got one starting June. I've used it a couple of times so far. The rate is $30 for 3 months. There's also a deposit for the key (another $30). There is also an annual rate for $100, I think.
Also, if the Translink website says all the lockers are spoken for at a site, that might not be the case. Deal directly with C-Media. They told me of a location that had a spot open even though the Translink site said otherwise.
I have not come across of any theft with these kinds of bike lockers. I like that my bike is out of sight, secure from vandalism and being banged by other bikes on the racks. Well worth it, so far.