The problem is that oil company C can't afford to lose 30% of its profits, so it'll go out of business or be bailed out (of course, bailouts would be very likely if A and B took out default swap insurance policies on C going under, who itself netted out swaps on A and B going under, obviously).
Another problem is it raises the bar for oil company D to enter the market. So, yes, big oil likes Cap & Trade because it makes competition scarce. All big energy providers want Cap & Trade so they can "stabilize" their market. But really, "stabilization" is code for what I call "a fettered market."
So are you willing to act in defiance of Cap & Trade? Clearly, since the system doesn't work, we should work outside the system. If the market is regulated, we need an unregulated alternative. The advantage we have is that we don't have to worry if it's "green" or not.
As an example, one way to do this would be to buy a whole-house electrical generator that can run on multiple types of fuels (not very green sounding, which is good). My grandfather installed one of these in his previous residence, and it was pretty cool. I believe it could be configured to run on gasoline, propane, and natural gas. The natural gas option meant he could theoretically run it indefinitely.
Obviously, this would require a change in life style. Merely installing a generator isn't a silver bullet. But if the economics work out, it could be a smart move.
My grandfather got this generator because the place he lived would have frequent power failures in the winter. He wasn't thinking of political defiance. Nonetheless, having a way to go off grid or partially off grid would create competition for the electric company who is itself (voluntarily) hindered by Cap & Trade. In addition, the ability to run on propane also opens the possibility for "alternative" methods of trade.
For most, it could come down to a mere matter of economics. Is it really more cost effective to produce your kilowatt hour for yourself or allow the regular fettered market to do under heavy tax. If the cold hard numbers are the only thing anyone looks at, it may or may not be enough to justify the act. But it might be good to also go one step beyond the math and looking at this alternatives as a form of defiance.