OK.
Tried and tested. Works 100%.
Contributors.
Wir, Koaslord, Skapie, Oknar, Me and Denom.

Step 1: Open console and type "callvote changemission hospital_vs"
Step 2: Join the survivor team.
Step 3: Survivors kill AI and then themselves.
Step 4: Teams swap automatically, repeat above step
Step 5: Let the server load the new map
Step 6: Callvote return to lobby
Step 7: Join server from steam group servers or openserverbrowser console. Not from the lobby.
Step 8: Enjoy playing

PS. The easiest way to tell if the server is fixed, is to talk... if players on the other team can hear you, then no its not fixed. Or if you can only callvote from the menu to change to 2 missions.