E.B.,
I agree that the Information Path is a little Slow and has Gaps, but I will say it is better than No Disclosure at all and starting from Scratch with an Empty Scanner. Using the Uniden SC-230, I will verify all Frequencies that are Published, Note T/C's and then get on the Hunt for New Frequencies by Locking out the Verified Frequencies as I search. This usually results in a few new Frequencies and a more complete list. For example, I have the #1 Paul Miller Car listed as 452.7000 as I discovered that both Team Cars use Repeaters so I listed the Output Frequency but the 457.1000 seems to be a Pretty strong Signal to begin with. Some Years ago the Paul Miller Team use a Cross-Band Repeater the Operated in the 150MHZ Range. Other Teams started using this Setup including the 3 Car Penske Team at Laguna Seca but this Configuration didn't last long, most likely due to IMSA Rules. As for R.E., they did Update the Michelin Challenge List on the Friday Morning of the Laguna Seca Race which put me in a good position to put together a more complete list. Strangely, I didn't get all of the Cars so there are some Gaps. Chad B. with R.E. actually crossed over from R.R. and followed the IMSA Program when R.E. became more prominent.
Regarding the IMSA Rules for Radio Communications, the basic standard is that all Communications must be in the Clear and can be heard with a Scanner. There are Teams that use European Digital Frequencies and are covered by an FCC STA Grant filed by MRTC to allow the Frequencies to be used and to provide a Re-Transmission Signal for IMSA to Monitor. As IMSA is a NASCAR Series, the Bulk of their Radio Communications is Digital with the exception of the Main Race Control (461.2000, DCS432) and a Backup (464.6000 DCS631) for Team Monitoring. I have attached a snip of the IMSA Rules where Article 14 details the Radio use also and the MRTC STA Info. I hope this is Helpful.
BD