Sharing my experience when I worked at a major US airline and non revved frequently...
Employees at my airline did not usually commute on NRSA, they usually flew NRPS. That being said, sometimes F/As from other airlines had to commute (say a F/A from "X" airline needs to get from AAA-BBB for his/her flight, but only "Y" flies that route), and they were NRSA. Even when I was traveling on NRSA for leisure, I would be of higher priority than him/her since I worked for "Y" airline. I have been put in F before and the F/As were put in Y. It also appears that pilots had higher priority than F/As. But F/As at my airline had higher NRSA priority than me, since I was on personal travel.
THere is no major US airline that I know of that allows PS commutes. It is almost always done SA and at the same priority as someone on leisure travel.
At my airline, personnel of certain rank (managing directors, directors, execs) automatically had higher boarding priority when flying NRSA than other employees. A sort of "benefit" that comes with their job. There are also numerous boarding priorities (over 50, IIRC) ranging from emergency travel, death in the family, repositioning, training, deadheading, employees from subsidiary/parent airlines, etc.
When flying for business travel on my own airline, I booked "business travel," but I'm sure the boarding priority gave me a revenue seat--I was able to select my seat and also standby for an upgrade. However, these upgrades are frequently never realized because "business travel" upgrades are processed AFTER elites. I also earned miles for these flights. They are booked into revenue fare classes (usually full-fare) and while my name always showed up on the standby list, it automatically had the seat I had chosen.
You earned miles for nonrev business travel? Again I do not know of any major airline that give miles for free tickets employees use.
When employees at my airline flew NRSA for leisure, they were ranked (including those in their party on the same itinerary) by their boarding code (director or non-director, etc.), and then within those codes, prioritized by the year they began working for the airline. Tiebreakers rely on check-in time. As a non-rev, I always made sure to check-in at T-24 when check-in opened; I've frequently beat out other people who were hired the same year as me.
Most US airlines use the actual date of hire as the priority, not just the year.
On other airlines, I had to purchase standby NRSA tickets, which were presumably below that airlines' own employees, though it depends on the agreements between airlines. Some airlines you are allowed to purchase one pass and standby for a premium seat, while other airlines only permit you to buy a J nonrev ticket OR a coach nonrev ticket.
An interesting story, but one time I was flying from AAA-BBB on "Y" airline (my own), and I was 16/50 on the standby list. 24 elites on the upgrade list. When flying NRSA I always book myself in F, because if there isn't an F seat available, you'll automatically get whatever Y seat there is. The flight was late getting out because of late arrival and the ground-handling was done by agents that were not from "Y" airline. I don't think they knew my airlines' regulations, and automatically stuck me in F, even though those in front of me were put in Y. I believe they can auto-assign seats (which takes into account what class you "booked") and I was put in 1A.
I remember the agents saying they didn't have time to upgrade all the elites and just to assign everyone seats quickly. An irregularity, but I didn't mind.
Sorry for the long post, but non-rev travel was a passion of mine when I worked there, and knew the ins and outs!