I do think most companies will managed to break even during this period especially if the income is going on everything else bar the wages. On certain routes your still getting the same amount of money for less freq service carrying fresh air ( at times I have seen some busy runs)
On top of that as you said TGW we dont know what coming down the road, but It's clear that some major income streams for this year have disappeared, in Scotland alone.. like Airports, Highland show, Edinburgh festival, rewind, Scottish Grand national, SSE Hydro events, Radio 1 big weekend, Kiltwalks. So there clear going to be some hits in profits for 2020/21... but it's also unclear if Working from home will become common place, its also unclear if the shift in new jobs will all disappear, like Amazon, Supermarkets etc a good number of these people still use the buses.
WE could have bad reseccion then suddenly have the biggest boom in the economy ever, however that will not help any bus company recope the lost work as eg above.