The answer to whether Garands can fire commercial 30-06 is yes and no. Most commercial '06 would beat the hell out if a Garand and should not be fired through one. However several companies still commercially load '06 to WWII specs.
Additionally, you can install an adjustable gas plug in a Garand that will allow you to shoot any commercial 30-06. Its like a $25 part.
I suggest you check out the CMP.