Let's say that this thing in their pocket was indeed them being happy to see an Objective-C replacement.
On a more serious note, Apple has a practice of cooperating with a small selection of developers (who sign a bunch of scary NDA's) when testing new technologies.
It's certainly the case that some folks get early access, I don't really think that was necessary to make this happen so quickly. I'm not saying they didn't have early access, just that they...
1) already had a code generator for Objective-C
2) already had infrastructure for alternate code generators (they also support C#)
3) Swift and Objective-C share the same libraries and have similar semantics where it counts
4) Writing code generators isn't really all that difficult
It's perfectly believable that they banged out enough of a first-cut at this to make an announcement within a day or two of the Swift release.
You know Swift is just so natural to both Objective-C, Java, Scala, C# etc. devs already, and so much simpler than Objective-C, I have the feeling we'll see the fastest adoption of a brand new language in the history of computing here.
The graphics code they generate is mostly just using these CGContext APIs: https://developer.apple.com/library/ios/documentation/Graphi...
Mapping to the Swift counterparts should be straightforward.