Hi Wayne and all,
Sorry if these guys have you confused by now so here's my SIMPLE answer to your question.
"So, it would appear the base station with 100 watts output is not transmitting on the input frequency to the repeater but rather direct on the repeater output frequency. Is this correct?"
This is correct because the "!00W output" transmitter is the repeater itself. There may also be a low power base station transmitting on the input, this is the control point. There are several ways a control point may connect to a repeater, a telephone line, microwave link or direct radio link but they usually employ high gain highly directional beam antennas so it's unlikely you'll hear dispatch on the input in any case.
"I know the mobiles transmit on the repeater input frequency and then the transmission is rebroadcast on the repeater output."
You got that right.
There are a few additions usually, the mobiles may transmit on the output thus bypassing the repeater should the need arise such as in the case of repeater failure. This simply involves shifting the transmit channel while leaving the receiver alone so they may also hear the repeater. There may also be one or more mobile channels used direct car to car that are unrelated to the repeater.
It's rather silly to listen on a repeater input which is why the frequencies usually aren't listed in the various web site databases. The place to go for full information (except PL and DPL tones etc.) is the
http://wireless2.fcc.gov/UlsApp/UlsSearch/searchAdvanced.jsp FCC ULS database search engine.