http://www.moddb.com/mods/call-in
Personally I think it's quite good, and the rating is quite high on mod-db though some people doesn't seem to have very high standards when playing mods. Which might be a good thing.
The best thing about the mod in my opinion is the explotarion, I love that kind of stuff and since it's not bad looking I hope you will enjoy it as well.
The worst thing is some bad placements of enemies, this is all because I just started mapping to make something nice, put some combine in and kept going.
After all. I made this to learn mapping in source and I think you can see a big difference between the first and last map Especially when looking at the vmfs ^^
In the end it's definitely worth a play through.
Download it from mod-db.
Cheers.