From: Living in the fair city of Melbourne, Australia
Some quick answers:
Regarding arty: the only possible interaction between artillery fires and supply is to bombard supply bases.
Attrition of supply transport columns is affected by:
1) The APer/AArm fires envelope of units, collated through LOS, resulting in a firepower value being assigned to terrain locations. These values are integrated along the route followed by the supply column to determine the total firepower poured on supply columns during its trip.
2) This firepower value is then modified by the training and experience of the Supply Base. The higher these values, the less likely to suffer casualties is the transport column.
SEPs are best understood static supply bases, with an associated type of movement (wheeled, etc.) and an unlimited number of vehicles. They aren't modeled as on-map units, so you cannot bombard or direct airstrikes at them and expect them to become less functional. On the other hand, you can interdict transport columns travelling from the SEP to a supply base, very much as you can interdict transport columns from supply bases to line units.
< Message edited by Bletchley_Geek -- 3/26/2013 11:41:35 PM >