Thanks to Matt for the video!   I'm going to start out by saying this is a work in progress. There is alot to do to get these conversions fully working, but I do plan on updating these regularly until they are fully functional.
 
What this is
This is a thread where I'll be posting progress and patches for firefight maps converted to multiplayer. Yes this requires a Jtag/RGH/DevKit. Everything except Unearthed and Installation 04 will require pre-loading.   Current Version - v0.3 Locales added for in_game_multiplayer_messages and global_multiplayer_messages v0.25: Multiplayer Globals and UI re-injected with the newest version of Injection Assembly to include stringids English locales for random_player_names and team_names added Monitor model properties revised to have shield vitality  
v0.1: Fly around in forge (no forging or editing existing items yet, monitor's bipd and null's hlmt, so low shields will beep when you're in monitor mode) Play infection. I briefly tested Gun Game and Double Agent since Teancum posted his collection earlier and those seemed to be working, but everything else requires gametype labels which would require full forging capabilities to add. After transferring the new maps to your console, you will find them listed as their firefight map name with "MP" before the name. I have it set up this way so they are all listed together and easier to find.
 
 

 
If you've read enough and want all the patches, here's a rar archive of them all.
Now onto each individual map...
 
Overlook

Download
 
Courtyard

Download
 
Waterfront

Download
 
Corvette

Download
 
Beachhead

Download
 
Outpost

Download
 
Glacier

Download
 
Holdout

Download
 
Unearthed

Download
 
Installation 04

Download
 
 
Finally, here's a link to the parent folder of everything on mediafire. New versions will be posted to the same folder.
 
Enjoy! Feel free to use these as a base for whatever mods you feel like doing. Just don't forget to give credit where it's due
 
 
Thanks to:
The Assembly Team for a great modding tool, and again for automating injection.
Lord Zedd for this post on porting UI and campaign maps to multiplayer (although you do need to null scripts for firefight ).
Akarias for briefing me on the essentials for firefight conversion.