I have tested days ago this campaign, reporting some problems on Mantis Bug Tracker, I don´t know if you have read it.
Here the info.
Tested on 27018 and 27019 server.
Same problem as previous version, game stuck or server crashed loading the map l4d2_planb3_v051 when the map l4d2_planb2_v051 has been finished.
Tested on 27017 Realism Server.
You can´t pick up shells to fire the howitzer.
So some plugin or configuration causes the problem on Realism and Coop servers.
Every server has a different problem, something different is involved in each problem.
Tested on GunGameMod server, campaign works properly.
P.S: I´m using a very old computer right now, so I can´t play anymore in the next 2 weeks or so, just web browsing, so I can´t test it.
See ya.