I guess all the companies I've worked for/known have been using A/C. Even when at airport where there was a restriction on APU usage of x minutes b4 start we've been using the A/C during those x minutes for PAX comfort. So as far as I'm concerned, there's always been a good reason: the FCOM (Boeing) said so.
Whatever the template says (I've never seen it), I wonder what most companies do, in my own experience OPEN is the industry standard for the NG.