AFAIK, there is no easy route. They're created as SSIS packages so I suppose there's a way to bundle them for install the same as other SSIS packages.
The only option I've found as far as "scripting" is to open up each step and click the "view SQL" button (or whatever it's called). But that's not the "real" script.
Personally, I just go with my own personal maintenance scripts and don't use the maintenance plans. (Mostly because they're not really scriptable and not as customizable as I like.)