I'd be very surprised if all the relevant ticketing/interline agreements are in place yet
They are. I flew BM/LH on a BRS-FRA-BKK-BNE-BKK-FRA-BRS in October last year. One ticket, issued on 220 (LH) stock. Bags interlined, boarding passes issued, no problems at all.
What was missing was the ability to book using an LH flight number, and visibility on the LH website. (I had to piece the itin together and get a TA to ticket it). That's what the codeshare actually brings - a presence back on LH's network, without the convolution of going BRS-(LH)-BRU-(LH)-FRA.
That said, LH haven't loaded the codeshared flights to the GDSes yet. And it doesn't look like you'll be able to book BRS-FRA/MUC by itself via LH, as there's no LH fare been filed as of yet.