Breaking into someones house and discharging 70+ rounds of ammunition is an 'activity related to SWAT' and would land any employee of $DEV_SHOP, Inc. in jail, why are these corporations any different?
It's possible for a cop to have an off-duty job just as much as it's possible for most other government employees to have a hobby (and possibly get paid for it).
But these cops can't have their cake and eat it too. If while acting as a private enterprise they happen to come across a situation requiring them to act as an off-duty cop, then they should be treated as a cop for that situation, which includes liability to answer to records requests. If they're going to employ their public immunity to charges for some actions then they should be held to all the other responsibilities of being a public employee for that time.
I would assume you could query each individual agency as to how often their officers participate in swat operations, but without knowing how often the LEC was called, I don't see how you could get an accurate count of the total raids. Perhaps each jurisdiction would have to report how often they called the LEC into their jurisdiction.
They may be actually be legally right due to basically a technicality. Perfect for time for the state legislature to reign in the LECs and make open records apply to mutual aid agencies/agreements. I'm sure their representatives are jumping on that right now...