I'm not an employee, but as a former frequent flyer, this route is exceptionally competitive for revenue passengers on standby. Although there are LOTS of flights each day, flown primarily by AA, I wouldn't feel super good about getting on as a non-rev, even with the sheer quantity of seats. Being two large hubs for airlines means there are lots of frequent flyer elite passengers trying to change itineraries, get home earlier, etc. Add on to them the AA employees who would have priority, I assume for everything, it could be tough.
Reiterating that I've never personally done this as a non-rev, and the dynamics could be entirely different. Just thought I'd share my perspective from a past life.