In the case of Jaguar-Land Rover, the alternative was apparently Mahindra, and we know what happened the last time the British car industry was in the hands of a tractor maker.
From what I read in The Economist, JLR's business plan was apparently quite satisfactory and Tata intends to let them follow through on it unmolested. Rover had already turned the corner on profitability (more profitable than the rest of Ford combined, IIRC) and can sustain R&D on Jaguar's much needed new models.
I doubt MV is in such an enviable position, though, and I have to wonder how much oversight and direction it might receive from the parent company.
It's a very different animal from Triumph, which I am glad Mr Bloor shows no signs of selling... although, if worse came to worst, we could at least take some consolation in knowing that Mr Tata's first name is RATan.