Is bcg bladder cancer treatment effective or not?

Yes: Bcg is intended for use of "superficial" bladder cancer, ie, cancer that has not invaded into the muscle of the bladder (carcinoma in situ, ta or t1 stages). It has been shown to significantly reduce the risk of recurrence and progression vs. No treatment. There is some evidence that BCG may only delay progression--given enough time many people with high risk disease may eventually progress.

Yes: In fact after removal of superficial bladder cancer (not invasive), the standard of care is BCG injections in the bladder for 6 weeks. It is very effective in reducing recurrence.