Nope, it doesn't support DDE.
The only way the developers expected for external programs to control it was for WON, and that was with the DLL calls.
So the only other way to control OP2 is by manipulating the windows by generating messages (using SendMessage)
Another *really* good way to do it would be to subclass the window and control it with your own WndProc.
Well, there is a slight enhancement that the developers put in that I found, almost by accident:
You can launch the "SIGS" button/operation from the command line, or show the multiplayer window from the commandline.
To do SIGS/WON/whatever is configured in the DLL's:
x:\path\outpost2.exe /net:sigs
To just automatically show the Multiplayer window:
x:\path\outpost2.exe /net
I've tried stuff like /net:tcpip and /net:ipx, it doesn't work. Those are the only 2 know combinations that work.