It's been on several threads.

Short call out is 2 hours from call to airport report. 15 hour call block. 76 hours guarantee.

Long call out is 9 hours from call to airport report. Continuous on call; released for your 9 hours rest once called. 72 hour guarantee. Being an A reserve is essentially worthless as a commuter. They call you at 10pm for a 7AM check in and you don't live in driving distance of the base? Good luck.

Aggressive pick up windows occur each day 0900-1100 Local Base Time from Long Call (A) reserves and 1200-1300 LBT for short call (B) reserves.

Can only pick up a trip that matches number of days of availability, unless you are available 5+ then you may pick up 4-day trips.

An A reserve who picks up on the day prior to his reserve block is automatically released (i.e. not phone liable) until he shows for the trip.

A B reserve who picks up on the day prior to his reserve block or during his reserve block of days is still subject to a call block being assigned by scheduling to that pilot prior to his show time. Example: pick up a trip with a noon check-in, scheduling can (and often does) put you on a call block that goes from 0800-1159 as an example.

An A reserve can be converted to B reserve at scheduling's discretion.

Forgive me but what is the JRM you refer to in your post? Is that Junior Manning? What do you want to know about the policy? They can do it. If they call you and you answer your phone and are available they can make you fly something, but junior manning doesn't apply to reserves. The key word is "available." All the contract says is that you have to be available to be junior manned. You don't have to have an explanation if you are not available. You just have to say "I'm unavailable for that assignment." Then again you could also not answer your phone which prevents that from happening too.