If a forcewall is thrown around corner and a machine is covering down the corridor the forcewall landed, can the machine use the covering fire to shoot the forcewall even if the commando was not in view when it threw the forcewall grenade?
If I saw an object thrown around the corner and it was a forcewall, I would use my covering fire to try and destroy the forcewall right away, knowing it would block my cover fire. Of course, it will sacrifice my covering but it may help for the other machines to cover down the corridor.
Yes you can use covering fire to fire at objects.