On page 65, near the top, in the PRO-97 manual it says you only need the control channel for Motorola trunked systems. The SCE system is a Motorola Smart Zone or Smartnet as Radio Shack is calling it in the manual. This is a great feature as you can program many control channels from several different repeater sites into one bank in the scanner. When you are mobile or are not sure which repeater site will work best in a particular area, the radio will automatically select the best signal and use it to start tracking.
The SCE radios actually switch from one repeater site to another, and can do it several times, during the period a radio is transmitting or receiving depending on which site is being received the best. The PRO-97 will not do this. If it is using a particular control channel corresponding to a particular repeater site and you drive into a weak signal area for that site, it will continue to track and the reception will become marginal. Once the signal is lost entirely it will scan the control channels and pick the best signal once again. When I find a signal deteriorating during a reception I just hit the scan button again, and the radio then finds the best signal using another control channel and then the reception is improved.
For this and any other scanning, it is best to be acquainted with where the repeaters are located. If you dont understand the list in the database for SCE I can help as I've researched where each of the repeater sites is located. Some of them like Strawberry Peak and Box Springs are relatively easy to locate if you have computer mapping software like Topo USA from Deloirme. You just type in the name of the repeater site in a search and it is located for you, that is, if the name of the topographic feature is on their map. Others take a little bit more detective work usiing methods such as the USGS topo map software for each state or by typing the name into a Google search. If you get stuck on any name for the SCE system, let me know.