A bit more on the Canadian legislation relating to shareholders rights plans and takeover bids referred to in Dash's post, this excerpt relating to SRP's

Future Use of Rights Plans and Other Defensive Tactics

Although the CSA has not explicitly banned rights plans, we anticipate that their use as a means of blocking a bid or extending time will be extremely limited under the New Bid Regime in light of the new longer statutory minimum bid period. However, we do expect that rights plans will remain a relevant tool for purposes of deterring creeping take-over bids. Under both the current and new regimes, any purchase in the market that takes a shareholder above 20% ownership of the target company requires the bidder to make a formal take-over bid to all the target’s shareholders on identical terms, subject to two key exceptions to the formal take-over bid rules. The first is the de minimis exemption that permits a shareholder to acquire shares in excess of the 20% threshold through purchases of up to 5% annually at market prices. The second is the private agreement exemption whereby a shareholder may acquire shares in excess of the 20% threshold by way of a private agreement with no more than five sellers, subject to a price limit of 115% of the market price of the shares. Many Canadian public companies have rights plans not only because they want more time to respond to an unsolicited bid, but also to prohibit the use of these two exemptions to acquire control of the company without offering an appropriate premium to all shareholders. Such companies do not want any one shareholder or group of shareholders to acquire negative control by assembling a significant block (e.g. 25% or 30%) of the outstanding shares, which significant block could:

• prevent a bidder from acquiring two-thirds of the outstanding equity of a public company (which would prevent the bidder from squeezing out the remaining one-third at the same price paid in the take-over bid), thus deterring a bid that the target board and other shareholders would find desirable; or
• as a result of the minimum tender condition under the New Bid Regime, block a take-over bid entirely.

Notwithstanding its overhaul of the existing regime through the adoption of the New Bid Regime, the CSA has left its policy on defensive tactics (National Policy 62-202 – Take-Over Bids – Defensive Tactics (NP 62-202)) intact; however, in its notice published on February 26, 2016, the CSA took the opportunity to remind the market of its continued jurisdiction to examine the actions of target boards in specific cases, and in light of the New Bid Regime, to determine whether they are abusive of shareholder rights. While there is debate about whether securities regulators or the courts are best suited to review the conduct of boards in the context of take-over bids, we do not anticipate a revisiting of NP 62-202 in the near future, and certainly not until after the effects of the New Bid Regime are well understood.

Ability to Lock-Up Blockholders

The minimum tender requirement will also make it more difficult to use a take-over bid as a basis for acquiring one or more blocks constituting less than 50% of the shares of a target under a hard lock-up arrangement. Currently, a bidder can guarantee a locked-up shareholder that its shares will be purchased by the bidder even if the bid is not accepted by a majority of the shareholders. This will not be the case under the New Bid Regime.3

Complete article here:

http://www.canadianmergersacquisitions.com/2016/02/26/canadas-new-take-over-bid-rules-seek-to-level-the-playing-field/