as of now you can only use our NTRIP implementations.
So the raw messages (RTCM or CMR(X) etc) become part of the protocols we talk to our receivers (which differs between Trimble and Spectra). And we don't have a mechanism do funnel external data into the stream so far (at least not this way - and not periodically).
Actually the first time this gets requested.
May I ask where the benefit is (from your point of view) is.
If we understand the goal/ workflow we may be able to help (although it may take some time).