Aircraft such as Air1 or Star1 have many radios in their cockpits. I recall Dann Shively formerly of KCRA, mentioning this over-the-air many times. You've got one for your work (the LE or media channel you are on), you've got one for general aviation, and often one for air-air traffic (which is what 132.125 is).
The answer to your question depends on what you want to hear. For me, it is monitoring any frequency where I expect they may be. It typically means a good antenna and multiple receivers so as to not miss anything.
If all you are interested in monitoring is one of these aircraft, good luck. You pretty much have to be on the channel where they're being used to follow along. That means whatever TG on SRRCS, CHP (several local channels), media (case for Live Copter 3), various simplex frequencies, and of course Metro air to air 132.125. Keep in mind the actual channel you hear them on will contain the type of traffic for that channel. For example; air-air is for co-ordination between multiple aircraft that are flying in the area. Aviation channels are for aviation purposes (co-ordination with other aircraft). LE channels are LE activities and so on.
