My understanding (at Bmi at least) is that you can pay a bit more for a Business standby ticket, so the issue is not that staff shouldn't be up there, it seems to be that you have to pay more to get up there.
Like previously, UA allows (appropriately attired, and with fairly comprehensive 'rules' and guidelines) it's staff to sit up in C or even F class, but you pay more for the privilege than flying in Y.
So if the same programme that used to exist at bmi is still in place, you CAN sit up front, you just have to cough up a bit more for the privilege, and I don't think that's too much to ask.
In any event, when I was working on the bmi longhaul product design etc, there were a number of managers (SG comes to mind) who were adamant that staff should not get to go up front at all as they 'detract' from the product. While those views might have made Cabin Services management so strict on on board upgrades, I'm glad that someone in staff travel was decent enough to make it possible for staff to travel up front (provided they pay for it).
At BA, I understand you don't have the option to even pay more for C class, and if it's calculated on ID90, then you're paying quite a bit more then bmi staff pay on the service charge tickets.