Can't speak for west coast procedures but if you venture further afield there are differences across the FIRs. Many e.g. Gander/Shannon, don't demand any pilot initiated position reports at any stage unless the automation doesn't work. OTOH the Aussie FIRs always do demand a initial position report - and they will ask for it via the CPDLC. Generally in most parts of the world you simply log on, do the Selcal check and that's it ( though you may get a CPDLC ping asking you to acknowledge on some oceanic routes for FANS purposes). The CPDLC/FMC should silently handle the position reports, at the FIR boundary you switch to the next FIRs frequencies, do a selcal check and again, that's it.