Welcome to the Forum!!
BCG is absolutely the best current treatment for CIS, so it is well worth your efforts to have it. Remember that it is NOT an active TB agent, but one that was modified in the laboratory many many years ago to use as a vaccine in children. It is, however, a live bacterium, so caution is advised.
You ought to be fine as long as you are careful...washing hands and everything else carefully after use and using disposable, one-time-only catheters for this.
Of course, your doctor is the one to give you definitive advice on how to handle this.
As someone who had CIS and BCG, and is now almost 9 years cancer-free, I wish you the best of luck!!!
Sara Anne