How can it ever be in the national interest to allow a foreign takeover?

With Newmont Mining Corp's buyout of Goldcorp Inc., Canada has now lost its two largest goldmining companies in quick succession (just a few months ago, Canada's Barrick Gold technically bought out South Africa's Randgold Resources, but it was, in effect, a reverse takeover, as management of the combined company was handed over to Randgold executives and Barrick's Toronto headquarters was gutted - a strange deal that I never did understand).

The phrase "hollowing out" is being bandied around again, just as it was ten years ago, when much of Canada's heavy industry was sold off (think Inco, Falconbridge, Alcan, Dofasco, Stelco, etc), not to mention other iconic Canadian companies like Hudson's Bay, Molson, Fairmont, Four Seasons, etc. It does seem like the country has lost control of an awful lot of its industrial powerhouses in recent years. But what does that actually mean, and what practical effect does it have on the country when a Canadian company is sold abroad?

Foreign mergers and acquisitions (M&A) do come with mutual advantages, whether from economies of scale, shake-ups of supply lines and management styles, improved productivity and R&D strategies, etc, etc. They have to, or such deals would not be struck or even mooted. But there must also be drawbacks, no? Under the Investment Canada Act, all major foreign takeovers are subject to a government review, and the final decision on whether to allow a takeover - essentially whether the deal would be a "net benefit" to Canada, from the point of view of employment, productivity, competition, national security - rests with the Minister of Industry. Some mergers are disallowed (usually from a national security perspective), but most seem to go through.

A major 2008 analysis of "corporate takeover effects" (CTEs) by the Conference Board of Canada called Hollowing Out - Myth or Reality? concludes that CTEs on acquired companies are typically "positive for shareholders, mildly positive or neutral for operations, capital, people and community involvement, and negative for governance". It also maintains that "there is no evidence of any decline in the overall level of head office employment in Canada" as a result of foreign M&A, which I must confess surprises me.

Surely, there must be more evidence from elsewhere - that's what the Internet is for, right? A 2014 German report on the impacts of foreign takeovers suggests a negative impact on employment and no productivity improvements to speak of, although it also notes that these findings are a direct contradiction of previous German empirical evidence, so it is not clear which evidence should be believed. A couple of years ago, the Dutch government put forward new rules that would hinder takeover bids by foreign companies, so they must have been convinced that foreign takeovers are bad in some way. The proposal met with almost worldwide condemnation, and dire warnings that it would put the Dutch market "in an unfavourable light" with foreign investors. After that, I start to struggle; there seems to be less evidence, on either side, than I had thought.

These reports are all well and good, but they are inconclusive, and they don't really answer my questions. How can it ever be in the national interest to agree to a foreign takeover of a major company (especially an iconic one)? My impression is that, after every takeover, there are a whole load of redundancies, usually as a drastic cost-cutting measure, but also to avoid duplication of core services. And wouldn't there also be a substantial loss of tax revenue as profits are repatriated elsewhere? It has not, though, been as easy to find out as I had anticipated.