Sorry that i missed this.
Yes, the poster system does not decompile the map. Otherwise your client would be downloading a new map each time the posters changed! Also, if it wasnt given a custom map name, it would render our posters on other servers!
It is an additional system that we have in place. We manually define where we want posters to appear and then image files are put on those placeholder co-ordinates.
Hope this answers your questions.
The Programmers Mantra: Declare Variables, not War.