Hi Mer
OML cut = BTS down
yes, OML is used for supervision but it also carry signaling, (no signaling=> no traffic). the behavior of BTS was good because O&M is up but if you restart BTS (switch off an on) you can see that your BTS is down.
you said:”OML was down because we had a faulty card in the BSC” = if BSC can’t control BTS = 🙂