what are the rules governing cards that are placed in the play area during scenario set up that wouldn't normally be put in the play area?

cards like

Sniper Attack in the Liberation scenario. [ command cost 1, action phase: Choose an enemy squad within LOS of any friendly unit and roll 3 dice. if you roll at least one 6 result immediately destroy one figure of your choice from the squad]

sustained blanket in the Siegfried Assault scenario [command cost 2, action phase: establish contact 4, target hex, determine drift, suppressive area attack 4, suppressive wide blast radius 3]

Bombing Run in the Siegfried Assault scenario [command cost 4, action phase: establish contact 4, target hex, area attack 4, wide blast radius 3]

Anti air support Siegfried Assault scenario [command cost 1, action phase: discard one of your opponents air support strategy cards that is face-up in his HQ area. or. your opponent immediately loses up to 2 available command]

I asked this question on another topic, about the Liberation scenario, but i think the question deserves it's own topic and it's own answers/discussion as this situation, i've discovered crops up in numerous scenarios. It's something that is not covered in any rule/scebario book

I have always seen this as if they were pre-paid and ready to use. Just place them in your play area in stead of HQ, and play them as an action as normal.

My thoghts are going on the same way as Hefsgaard said above.

Well i played the Liberation scenario with the sniper card as a free, non discarding, one action card. (so i could use it up to 3 times per turn, expending an action each time, providing a non fatigued unit has LOS of course)

Huge difference, the American player surrendered, after failing to take even the bridge for the extra rienforcements. the sniper crippled his forces even when he laid smoke. (due to having LOS into a smoke hex, but not through it)

My friend found it very frustrating. we are going to have another go at it as i assured him there must be some strategy to advance to the bridge while protecting his troops against the snipers and op fire.

I placed nearly all of my german troops near the bridge (legally as near as possible) so after turn one i had the half track on the bridge, with a machine gun squad and two anti tank squads in the forrest hex another machine gun squad started in op fire mode covering the bridge approach and the mortars behind a hill within range of the bridge and surrounding hex's.

the trouble was i placed the machine gun squad in op fire so every time it fired it wasn't fatigued which allowed it to be a spotting unit for the sniper card. its a very hard combo to overcome.

The ability to use a sniper without discarding it sound like it over the top- why spend actions on anything else? Just snipe with every action.

I am not sure if the sniper actualy requires the spotting unit to be non-fatigued?

yeah the card says " in line of sight to a friendly unit" the rule book states only non fatigued units can give line of sight.

To my knowledge only Mortars state that the 'spotting' unit needs to be Non-fatigued. The rules section on LOS says nothing about the state of the unit(s).