Generally speaking, urologists are experts in urology (particularly surgery for urological conditions) and oncologists are experts in cancer treatment so it stands to reason that the onco knows more about treating your husband than the urologist does. In most cases, once the urologist knows that PCa is incurable, they hand the case over to oncology unless there is still some specific thing that they might need to be involved in, in your case the possible TURP but in other cases, managing permanent catheters, frequent UTIs, etc.