I can see where it could appear that there was $$$ to be made.
However basing a business model on the accounting methods of another company that you will have no control over doesn't seem sound.
Once you invest millions on the infrastructure they could just add a clause to the electricity prices limiting the large peak period feed in rate to just the first say 30kW.
This wouldn't affect most individual customers home solar feed in set up but would eliminate any profit from your business.
Or as more people put solar on their roofs they may drop the feed in price. That is what happened here. The government let a collection of senior executives from various electricity companies get together and decide what a "fair" price would be for feed in during peak periods. Surprise, surprise they decided that a bit less that the wholesale price for off peak electricity would be a fair price. We went from a 33 cent feed in to a 6.5 cent feed in. Off peak supply price is about 13 cents and peak supply price is about 34 cents plus another 6 cents if you want electricity from a renewable source. Must be hard to make a profit with those figures.
Also as mentioned, the buses need what they charge up with at off peak rates to actually drive around. So there would be no surplus to feed back in at peak times.
As for using them for emergency power during a disaster. I would expect all available buses would be getting used to move people around rather than sitting plugged into a building.
Also once the buses charge ran out it would be impractical to attempt to recharge it in situ. And with it's charge depleted it won't be going anywhere under its own power.
For emergencies a big diesel generator with a big fuel tank mounted in a standard shipping container form factor is the easiest to move long distances and the easiest to refuel in the field.
The only use i could see the buses being put to other than being a bus would be as a load leveller. Connected to the grid and supplying some power for short voltage sag events where the bus can be quickly topped back up after the grid recovers. Useful but not profitable.