You can also access maps with the ARCHIVE.EXE in your COH2 directory. The SGA files are huge and will create a lot of data on your drive since it will unpack ALL of the maps in the SGA file. You can see from the command that the maps will be put in your COH2\DATA\scenarios directory.
FOR MULTIPLAYER MAPS (MP)
At a DOS prompt in your COH2 dir in steamapps:
archive.exe -a CoH2\Archives\MPScenarios.sga -e CoH2\Data
archive.exe -a CoH2\Archives\MPXP1Scenarios.sga -e CoH2\Data
Also available:
archive.exe -a CoH2\Archives\DLC1Scenarios.sga -e CoH2\Data
archive.exe -a CoH2\Archives\DLC2Scenarios.sga -e CoH2\Data
archive.exe -a CoH2\Archives\DLC3Scenarios.sga -e CoH2\Data
archive.exe -a CoH2\Archives\TOWScenarios.sga -e CoH2\Data
Some where on this site are the batch files that these commands came from.
The files you are unpacking are:
Located in your COH2\Archives directory.