And now I'm wondering where (if anywhere) we've seen Cass and Dick interact at all, outside that series (Thanks for borrowing Dick, Beechan!) and on issue of Bruce Wayne: Fugitive.
There was the issue of Bruce Wayne: Fugitive where Dick and Cass played out Vesper's murder (the one with the cover of "ohnoes Dick is going to shoot Cass eleveneleventyone"), and the issue of Nightwing - I think #81 - where the Batfamily came to visit Dick who was in the hospital after his latest skirmish with Deathstroke, and he asked Cass to check on Deathstroke for him. And she did, and there was a lovely parallel of confrontations between Dick being interrogated by a Nosy Reporter type and Cass fighting Deathstroke. And in Gotham Knights #45 there was one page and one panel with significant Cass-Batboys interaction. Aside from that, I'm not sure.