Whether an ECN offers pre-market and after-hours trading or not depends wholly upon the policies of the company that runs the ECN. I don't know about the ECNs in the Canadian market, but I think for NYSE and NASDAQ issues, NASDAQ, NYSE Arca (or whatever they care calling it now) offer extended trading. I don't think BATS has trading after the close, but they may have it before the open. Direct Edge may have some trading outside of market hours.
Extended trading hours might add about two additional hours of trading after the close. Before the open, depending upon the ECN, one can place orders and trade up to two or maybe three hours before the official open. In both cases, the trading volume is typically pretty sparse. Most extended hours trading takes place close to the beginning or end of the trading day. In general, I wouldn't recommend trading outside of normal hours, and I probably wouldn't use a GTEM order type. If you place a GTEM limit order, and it is close to the market price but doesn't get filled during the day, I question the value of getting that order filled after hours. Anyone desperate enough to remove liquidity after hours probably got stuck in a bad position that they needed to flatten and they are clearly willing to accept a bad after hours price.
Also, it is totally up to your broker as to whether they offer certain order types, regardless of whether the exchange or ECN offers it. Also, not all brokers will connect to all ECNs. Every broker's access to the market is a bit different depending upon the deals they cut with their carrying broker (if they are a small operation) or the exchanges/ECNs (if they are a large operation). So, if your broker doesn't offer certain order types, they may just be too small or too cheap to pay for top level service from the exchange or ECN.