You're most likely correct that a sat./OTA diplexer would prevent "interference" between the cable internet and satellite signals and I stand corrected on that point. But almost as bad instead it may prevent proper reception by the modem of the cable internet signal for DOCSIS 3.0 standard signals. As for a a similar DSL "training signal" phase for cable internet service I doubt that since whereas DSL uses a point-to-point type topology, DOCSIS for cable internet systems is a point to multipoint type where the CMTS at the CATV headend chooses the particular downstream and upstream frequency that many subscribers in a group use on a time-shared basis. Therefore if one of those subscribers assigned to a group with a given down/upstream frequency and is unable to receive the downstream signal because of a SWiM sat/OTA diplexer in line with the modem which blocks it, then that sub. will simply be SOL, and just not able to access the network. I know of no provision in the DOCSIS standard for the CMTS to make a special accommodation and change the downstream frequency just to suit one subscriber in a group with a reception problem caused by a component on the customer's premise. .