Jude - other than Sara Anne's excellent advice, here are a few other thoughts.
First, prostate enlargement is usually treated prior to the procedure with a drug called tamsulosin (which relaxes the muscles in that area). Do you recall whether you received such a drug beforehand, either orally or intravenously? I have some benign prostate enlargement myself and after one dose of that, I found I could urinate better than I had in years.
Second, if there is a stricture (which usually means scar tissue partially blocking the urethra), that can be removed ("ablated") and my urologist told me that if I develop such a condition, he would recommend removal to minimize the change that the urethra could become fully blocked precluding urination, obviously a very serious condition.
Finally, the size of the catheter used for the BCG is 14 French (3/16th of an inch) which is 1/2 of the size used for the TURB (28 French - 3/8th of an inch), so it is indeed unusual for a stricture to obstruct such a small diameter catheter. If your urethra has unusual twists or turns, that is another matter - I can't comment on that.
Good luck to you!!