But the priest can say mass only in consecrated space.We've had Mass held a couple of times in our home. And there are sports teams whose chaplains have held Mass at airports as the players awaited their flights.
We can say mass anywhere. It’s being allowed and recognized is a different case
As an evangelical I don’t know the detailed drill, but I’d guess they would want some sort of blocked off area for the duration of the ceremony, dedicating its use for that time (you don’t have cars driving through, people walking through etc., distracting from the intended worship). The same would be desired for an evangelical worship service for obvious reasons.