Well what I did is installed esf 1.2 on my steam acount, then for LAN I used WON with esf 1.1, how I did this:
I installed 1.2 like you all should, the normal way, then with 1.1(WON) I installed Half Life on my friend's pc and installed 1.1 on there, then afterwards I just copied 1.1 from his pc to mine, so then we can play against each other without him needing steam or internet. But I don't think there's a way to make both work with steam though...
I hope this helped you a bit.