BCG is the current "gold standard' for high grade, non-invasive bladder cancer...especially for CIS. There has recently been a world-wide shortage of BCG and other agents have been used. This shortage is apparently easing. I would wonder if the doctor recommending mitomycin has been unable to obtain a supply of BCG? I would certainly ask the reason for his preference.
Another area of concern in the path report is the mention that the cancer appears to have infiltrated the lamina propia, the first layer below the bladder lining. The report also mentions that it has NOT reached the muscle, which is good. But it is very important that he receive the very best treatment and as soon as possible. Unless the second doctor has a compelling reason, BCG is what is usually used.
Best of luck to your father, whichever treatment he deems best
Sara Anne