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It's okay, I know exactly what you're talking about.

OK, let me completely edit this post, because I saw the movie today and watched the Twilight Bark carefully.

First, the Scottish Terrier is indeed Jock. He barks up the drainpipe to the Afghan hound, "Prissie," who lives in her artist owner's apartment. (They were the first pair walking down the street that Pongo had checked out in the beginning and considered as mates for himself and Roger.)

Next up, you see Peg and Bull in the pet shop window, with all the pups. (Peg is waking up in her bed.)
There's the fancy Poodle whom Pongo had also checked out, who hops on top of the vehicle to bark, and so on until...

Old Towser, the Bloodhound, hears the message. Towser IS Trusty, with different colors. And that Scottie IS Jock, and Peg and Bull ARE themselves. What I mean by that is, their animation is taken DIRECTLY from Lady & the Tramp. You can see it if you really watch them moving.

In Patch's London Adventure, while Thunderbolt is having his "heroic bark" audition contest thing, there's a Scottie again who looks like Jock, as well as a Sheepdog resembling the Colonel and a rough Collie resembling the one who aided the Dalmatians in the first movie. In all likelihood, that's who they're all intended to be, but the newer/modern animation style has them looking a little bit differently than in the older, classic 101D and LATT style.
Not to mention that Prissie shows up again, amongst the crowd of random dogs gathered outside Thunderbolt's trailer. And who knows how many other little cameo references there might be. ^^

Anyway, related fact: Peg, Jock, Trusty, and Pongo (or at least, a Dalmatian who's probably supposed to be him) can be seen during "Why Should I Worry?" in Oliver and Company.