As you certainly know this ticket/season is only valid on R/RE-Zuege. There are no through R/RE-trains between the 2, always change Ulm, Landes/provincial border, and perhaps also Augsburg. In both cities are various R/E trains loco hauled, mostly with double-deck coaches, but right now I have forgotten if these also serve these direct lines-they did from S via Ulm-loco change!-till last year going to the Bodensee/Friedrichshafen, but this later part is now also electrified.
A novelty for this year, but no loco, is the hi-speed line S-ULm, now partly open, from Wendlingen and also with a RE-hourly service, but sets.
In B-W=Land Baden Wúrttemberg, around Stuttgart, are several partly weekend/summer only small branchlines with special old stock also open for these ticketholders. S-main station is a big building site. Take extra time to find your way around it.
Just by chance right no sitting in dismal (sorry to say) MAN airport, awaiting an EZ-flite to M(ünchen), to continue my current InterRail.