I just had a quick search on various dates to the end of the year, and BRS-BRU is showing the BM-marketed and operated flights using the ER145s.
It was a year ago (29OCT17) when BRS-BRU surprisingly switched to being a BM marketed and operated route with an SN Codeshare (https://www.pprune.org/airlines-airports-routes/600014-bmi-regional-3-a.html#post9927670)
As part of that discussion, it was suggested it was a temporary change, so maybe that arrangement might be ending, and SN are going to work it directly. That might also explain how BM are finding ER145s to put elsewhere. (NCL-BRU going 3x daily with an ER145 for example). On the other hand it could just be a glitch where someone forgot to update the flight data after a year. The reference to 85s suggests it might be.
I'm hoping that that SN will be back as BRS sole Star Alliance airline at some point (or that BM rejoins, however unlikely). At the time of the last change I was disappointed that BRS had fallen off the Star network, not least because there were no miles redemption options.