With my extensive testing with these units here is what I have learned:
They will not fire while they are moving.
They also have the ability to shoot Harms down while the Snowdrift is up
The tactic that I have been playing around with takes two pilots and using a Hunter killer tactic with Standoff weapons.
The key is to get the SA11 or SA17 to track you(SA11 15 miles and the SA17 20 miles) .This gets them to stand still which gives the second pilot the ability to launch SDBs or JSOW on the units.
It has worked in TE’s but have not tried it in Campaign yet.