Like CPZ said above, just because you're cleared in CASS doesn't you can ride in a certain carrier's jumpseat. It all rides down to the each carrier's respective reciprocal jumpseat agreement.
Let's get realistic here: CASS/jumpseating is NOT a flight benefit! Flight benefits are the benefits bestowed by the airlines to its employees as a goodwill gesture as a "thank you for working here, we can't pay a decent wage, so here is a how we make up for it." Flight benefits are when you can take your parents, significant other (wife, domestic parents, etc.), children, BUDDY PASSES, etc.
Delta has one of the best employee pass travel programs around. Sorry, Pinnacle, you got the short end of the straw when you negotiated with Delta on your pass program (no buddy passes, limited international travel in BusinessElite). One of the worst employee pass travel programs: United. Getting rid of buddy passes and designating either 1 or 2 friends as your "travel friends" for 1 whole year at the cost of $100-200 depending on the number of friends. Yeah, no bueno.
As for supplementals, each carrier negotiates their own contract with each respective carrier. When I started with RIA in 2008, we had an ID90 agreement with NW, and ID90 agreement with TZ (for all you newbies on this forum, that was ATA, they went TU in April 2008), an ID90 with NKS, and one with SY. The one with NW; when they merged with DL, DL honored that agreement until 12/31/2010; when RIA had to renegotiate it. RIA's "glorious" mgmt figure that DL would auto-renew the agreement...but we found out the hard way when several employees were bumped off a military flight in HNL due to payload in 2011 (I was one of them...I had a way out, because I had CASS authorization, but the others didn't). I went to the DL counter to check on our DL pass privileges, that's when we found out! When I left RIA in 2012, we only had benefits with Spirit as a company as a whole. Big difference from when I started!