Possibly. It depends on what the VPN does with the ports, ie, the remote endpoint with the public IP address would need to send the packets to RE with a local port of 80 for RE's server to respond to it (ie, 1:1 mapping just like a non NAT444 connection). If it doesn't then RE won't respond just the same as for NAT444. Finding info on how the local port is handled is proving to be a bit difficult; it'd probably be easier to just set one up and see if it works.
There are two other things that could be an issue with using a VPN, one would be latency (I don't think RPA is very tolerant of it.) and the second is some ISP's block VPN traffic!
- Tim