"If the TSX and London Stock Exchanges amalgamate, the TSX will own 45 % of the Group and hence control of Canada’s investment system and related regulators will be foreign controlled.Listed Canadian Companies could then be beyond the jurisdiction of the Canadian Government and at the mercy of Foreign investors with multi billions of dollars at their disposal."

I'm not sure whether that would absolutely be the case.

This article, for instance, suggests otherwise when it comes to regulation:

http://www.theglobeandmail.com/globe-investor/investment-ideas/streetwise/tmx-takes-on-the-misconceptions/article1938425/

Some big business leaders (including Jim Prentice) have raised concerns about regulation. TMX says there isn’t any reason to worry, because everything will continue the way it is now. As a reminder, the TSX and LSE will continue to operate as separate exchanges and the OSC and FSA in London will regulate them separately. (Same for the Montreal Exchange, which the AMF will oversee, and the TSX Venture Exchange, which will be governed by B.C. and Alberta’s regulators.)