Short answer is practically they would never buy a controlling stake without taking the whole company (at least not for long) because 1)it would drive up the share price of shares they did not purchase and 2)any revenue generated by the company would stay in the company and if they wanted revenue to flow back to the Pharma co they would pretty much have to do it via dividend which would then also payout to other shareholders. 

I forget what the ownership threshold is in Canada for requiring the purchase of all shares, but it's pretty high. 
JMO