Joe Baldwin is hoping to bring a native plant garden to the masses via a flatbed CTA car next spring.
Baldwin is talking with the CTA about all the details. A CTA spokeswoman said there is no agreement yet, but the transit agency is putting together a cost estimate. The CTA still needs more technical information and whether it's even feasible. Update: The cost for this would be borne entirely by Baldwin's group.
Some details can be found at the Mobile Garden site, including prototype photos like the one shown here.
Good luck on this. Seems like a cool, but possibly expensive project.