Wes, naturally - Cap's DSL was originally styled after rake, it's an easy mistake to make. Depending how you want to do it, you can simply `require` your `Rakefile` in the Cap script, (ensuring of course to include Rake, if that directive is absent from your rakefile), and then you call tasks with something like (and I'm working from memory here)
Rake::Tasks['mytask'].invoke
(there's also `.execute`, but check the docs for why to use one/the other) - and, check the Rake docs, anyway!
I hope that helps, if not - the easiest alternative, just shell-out and call it that way.