Yep, but the upgrade cert's can only be used by the cert owner and a companion. They can't be transferred to two other companions. So, I guess if that's what OP was thinking (and using his status to get a C+ seat), that wouldn't work.
Sadly I see no way around this, except paying C+ for the 3rd guy, which is probably what I will do.
But at least it looks that I can I purchase 1 economy seat + get a companion one for free, then upgrade both to Delta One using 4 regional upgrades, meaning 2 Delta One tickets for the cost of 1 economy ticket. I'm pretty sure it wasn't possible a few years ago.
Thanks.