Gonna disagree on this, not on the basis of the MA license to carry requirements (which are dumb, but a sperate convo) but the idea (presented by the article) that fired troopers somehow have more "rights" that they're entitled to.
That's not the case. For example, I'm a Federal LEO (for the BOP). I'm authorized under the LEOSA (LEO Safety Act) to concealed carry in all 50 states without permit, despite local laws. I can do this as long as I'm an LEO and once I retire/leave a LEO agency after 10 years of service.
My ability to do this is based on being in "good standing" though. If I get fired/resign my post for fighting local PD at a local bar's karaoke night, I'll lose my authority under the LEOSA. (That fight example is based on an actual situation with staff here).
This is from the State Department page, so it says "federal", but it's also applicable to state employment.
The bolded areas are the ones that apply here.
The officers were fired. The don't get special LEO privileges, because they aren't "qualified separated" officers.
Edit to add: I'm just now seeing that the article was written by a retired police chief. So his statement that
either means he knows less about the LEOSA than we learn literally the first week on the job, or he's lying.