Lena,
It is normal to do a TURBT if they find a tumor during cystoscopy. Your mom's urologist did not find a tumor.
If he took random biopsy samples during the cystoscopy, then he was being especially diligent AND your mom is especially tough because when they tried to grab a sample from me during cystoscopy I went through the roof.
Mike
PS: Yes, it is a good sign. Everything so far that the doctor has done has been a good sign. The part where he said at this point he doesn't think it is anything serious but just wants to run some more tests to be sure is a very good sign so far.
All you can do now is wait for the results of the various test that have been done.