Yes it's possible. I can create a port forwarding rule for 3389 on my router pointing to my laptop, and connect comfortably even with PocketCloud Companion installed.
However, both sessions will not run simultaneously, due to an RDP limitation in Windows. If you connect with one, then the other, the first will be disconnected. This is normal.
PocketCloud uses port 3389, just like a normal Remote Desktop Connection.
When you connect to the desktop using PocketCloud, it throws anyone else off the console (assuming it's not a Terminal Services Server) that is logged in with the same credentials.
I was able to log into my laptop running Windows 7 using PocketCloud on my iPhone. It took over the logged-in session on the laptop.
I then used my Mac to connect, using Remote Desktop Connection, and it kicked me out of PocketCloud. So it's all RDP port 3389.
As to what's happening on your router, it looks as though the PocketCloud Companion for Windows client is tunnelling a session through TCP on a different port. This makes sense, seeing that you sign in with a Gmail account.
I did a
netstat -a while connected using the PocketCloud client, as well as verification through Process Monitor from SysInternals), and I found this:
This coincided with Process Monitor, which found that the PocketCloudService process was talking on various ports locally to a remote port of 5222. For instance (edited for brevity):
PocketCloudService.exe 2056 TCP Receive MyLaptop:1171->pb-in-f125.1e100.net:5222