There's a difference between "canned" tracks or "backing tracks" and using "patches" the play the string section parts on a keyboard. If it's "canned," you're using pre-recorded parts. If you're using a string section or horn section "patch," then you're actually playing the music (and if you make a mistake, it will "shine through") using the keyboard. If you use pre-recorded tracks, there's much more danger of a problem (think Ashley Simpson on SNL a few years ago) because if the track is "cued in" at the wrong time, it will through the entire band off the rails. When Which One's Pink? performs "The Wall" (or songs from "The Wall"), we use patches. I'm confident that's what the Aussies do too.
I have seen Damian play keyboards too. To add a string and horn section would be too costly and take up a lot of stage space but it would be cool to see. 
