For what it's worth, we often use a business band frequency to send "pre delay" or IFB to a remote broadcast site when we're not using an ISDN line.
When a radio station is doing it's thing, there is there is anywhere between 7 and 15 seconds of delay before the analog signal is transmitted. (7 or 8 seconds for profanity delay and 7 seconds of HD radio buffer to match the analog and digital signal to prevent choppy blending.)
So, if a station is doing a remote, they need to hear the predelay on site for phone callers, music and studio cuing. Sometimes two predelay signals are sent, one with cuing (or IFB) and the other a mix minus, without the host microphone, to create a PA feed.
OK... that's my 2 cents.
Oh yeah, we always use our RPU channels. Well, most of the time.