I don't understand your question, simply because the Tories aren't in power - not at the present time, anyway. So with what authority is Mr Grayling "warning off" these companies?
Perhaps he's assuming that the next General Election will be a foregone conclusion for the Tories? Beware the ides of March! I seem to remember similar overconfidence in 1992 from a certain Neil Kinnock MP, Labour leader then, and of course what happened? The "grey man" John Major got on his soapbox (literally) and scuppered Kinnock and Hattersley in the GE that year.
Besides, what guarantees are there that the Tories would scrap the scheme in the event of them winning? Forgive my cynicism, but isn't the road to Number 10 littered with broken promises? Mmmmmmhhhhhhh..........