I know of some that may require a MA or higher. I am under the impression that for some high-profile technical writing, an MA would be advantageous.
It really comes down to what skills are required for the job. If knowledge carries more leverage, then an English MA would be the way to go. If experience carries more leverage, then an English MA could be skipped.
I think when you merge it with a hard science degree, the MA may carry some weight.
Pedagogy can be attained through certification (or a teaching degree), so no MA in English required there.