R3...has been used in the past during UPS/FDX/USPS peak season flying. I have done Airport/Hot Standby in ONT about 10 years ago. On one of the R3 days, we did go to HNL and got a 2-day layover in Waikiki out of it!

Rest of the Atlas system...R3 isn't a common practice.

facebook,
captainv is absolutely right...don't make this kind of decision unless you read this entire thread. Get a cup(several) of good, strong coffee or other adult beverage of choice, and make a go of it. This is likely the best (certainly the most current) thread out there about all things Atlas, but mostly focused on hiring, interviewing, and working at Atlas.
Good luck.