You can't normally add a background mask to regular text, so I would say no?
I think your only two options are to add MTEXT with the background mask option selected. Or add a wipeout to the block behind the single line TEXT.
I loathe the extra click required for editing attributes that are multi-line text. I suppose you could add a parameter that would allow you to stretch the wipeout to fit the single line text, but that's a few extra clicks as well.
