Complex sentence: All four stations refer to themselves on air as CTV, not by their call letters, and have common local programming for the most part, but are otherwise considered separate stations by the Canadian Radio-television and Telecommunications Commission (CRTC).
Split into simpler sentences: All four stations refer to themselves on air as CTV, not by their call letters. However, all four stations are separately licenced by the Canadian Radio-television and Telecommunications Commission (CRTC).