It's hard to quantify the potential loss of productivity or collaboration caused by working from home, though. No way to find out either, unfortunately.
But arguing around $1B saved won't be easy.
That’s about 0.6% of revenue for Google. Number sounds big until you put it in perspective and realize it’s just noise.
If people were even 1% less productive (in terms of producing revenue) then even that $1B saved isn’t profitable.
That said, there could be other arguments for expanding WFH but saving less than 1% of expenses is not one of them. It’s likely that the savings are largely due to COVID preventing typical travel anyway, which had nothing to do with WFH.