Hi,
AFAIR it's possible to run osmocom-bb "mobile" (GSM) and "modem" (GPRS) apps against that osmo-trx-ms with a B210/BladeRF underneath as an SDR.
It is related to work done with this grant: https://www.ardc.net/apply/grants/2021-grants/grant-paving-the-way-to-use-gs... https://osmocom.org/projects/cellular-infrastructure/wiki/GSM_in_70cm_HAM_ba...
Regarding GPRS, I was involved at the time with implementing the upper GPRS layers (RLC/MAC, LLC, etc.), which can be found in both osmocom-bb and libosmo-gprs git repositories.
IIRC only minimal support (1 TS TBF GPRS) is currently implemented, but it can already be used to tx/rx data over it with the "modem" osmocom-bb app.
You can find the GPRS architecture here: https://osmocom.org/projects/baseband/wiki/MS-side_GPRS
I'm not able to find more public information rather than: https://osmocom.org/search?utf8=%E2%9C%93&scope=&q=MS-SDR
Regards,