for my say in the matter, i dont think they can be painted or powdercoated BEFORE cams approval because the guy that looks at the welds needs to see that they are of good penetration, without that they would fail the cage. but after it would be fine
as for road use im pretty sure that you tecnically can only have a half cage installed, that is that no bars are allowed to be, beside or in front of the driver, for obstruction of vision reasons (thats a load of bull$#!t if you ask me)
which is just the same as no road car can have a race harness installed unless it is the crappy standard seat belt buckle 4 point type
thats my understanding for nsw regulations