Going back to my time in Oxford (the city not the Uni, as if that needed explaining) most of the rowing seemed to take place at silly o'clock a.m., early evening and obscure hours during weekends, when the Isis/Thames was less congested with idiots in pleasure cruisers (myself being one of the 'congestors').
The thing with the RMR is that you can realistically expect upwards of 20+ training weekends in a 12-14 month period, and weekly drill-nights early evening, just to complete training.
A "Team GB" rower maybe compatible once a 'trained rank' in the RMR but I'm absolutely positive the two are not compatible concurrently whilst a Recruit (Ooh, big words. Maybe I did go to Uni after all, but forgot).
Maybe for Regulars but for those in the Reserves who maybe a full-time student or have a full-time civilian job to juggle with home-life and RMR Other Rank Recruit Training before even looking at the demands of representing your country internationally, it's a bit of a time-management conundrum. Two missed RMR training weekends out of the 20-odd expected & you're back-trooped a year.
It may well be possible, but it's certainly worth being aware there are potential pitfalls.