I think this is more or less on the right track. I was looking over the Falcon schematics... they seem to refer to the LAN port as "SCC". So looking up SCC I found mention of SCC.PRG, which was exactly what you are talking about, setting baud rate of the LAN port.
A bit more searching yielded that SCC.PRG was part of a suite of apps called "HSMODA", by Harun Scheutzow. Here's a link to his page with source code for these utilities. Enjoy!