The case against the Energy East pipeline seems far from watertight

I have been trying to figure out whether an Energy East oil pipeline is such a bad idea, and if so, why.
The proposed 4,600km pipeline would transport crude oil from Alberta and Saskatchewan's oilfields to ports and refineries in Atlantic Canada (St. John in New Brunswick, as well as Montreal and Quebec City). TransCanada Corp's current plan is to convert about 3,000km of existing natural gas pipeline, and add to this 1,600km of new pipeline. The completed project would have an estimated capacity of 1.1 million barrels of crude oil per day, which represents an awful lot of road and rail tankers.
Now, I am not a big fan of oil and gas, and I am quite aware that we (Canada and the rest of the world) need to ween ourselves off it if we want to rein in destructive greenhouse gases. Having said that, the oil industry is not going to close down overnight, even in this new era of low oil prices. Large quantities of oil are still being pumped out of the ground, and this will continue for the foreseeable future even if we do start to act to reduce our reliance on oil and gas. So, we need to do something with it, preferably something responsible.
The Keystone XL pipeline to the USA is dead now (the US is gung-ho on becoming energy sufficient anyway), and the Northern Gateway pipeline to the west coast of BC is all but dead too after a recent ban on oil tankers along northern BC's coastline. Energy East therefore remains just about the only hope for the oil pipeline lobby. But it is beset by problems, not the least of which is the opposition, mainly on environmental grounds, of several key municipalities through which it would need to travel (such as Kenora, Thunder Bay, North Bay, Montreal), as well as of many of the First Nation territories on the route.
Opponents argue that converting the ageing existing gas pipeline would leave it prone to leaks and spills, which puts millions of Canadians and large areas of pristine wilderness and water at risk of a catastrophic spill. Added to that is the potential of a major oil spill from export tankers in the St. Lawrence Seaway, with its threatened beluga whale population. It is also argued that providing an easy outlet for Alberta's environmentally dirty oil sands would only add to Canada's already unsustainable carbon footprint.
But...
The alternative to a pipeline is rail transportation, which, as we know all too well after the catastrophic rail crash at Lac Mégantic in Quebec in 2013, brings its own challenges, both economic and environmental. And, while I am not too keen on the idea of exporting large quantities of this oil from Eastern Canada to overseas markets in Asia and elsewhere, bringing Canadian oil to the eastern part of the country would help to equalize the current east-west price differentials within Canada, and also reduce our reliance on other foreign oil producers. It seems kind of crazy to me that Canada is importing oil from unpalatable regimes like Saudi Arabia, when we are producing sufficient oil right here in the country (in fact we import almost half as much oil as we export, which is kind of like taking two steps forward and one step back).
So, which is the better option? I still can't decide. Is the environmental risk of a pipeline greater or less than the environmental risks of shipping it by rail? Dunno. Would a pipeline actually increase oil sands development, or would it have little or no effect on how much oil is actually produced? Again, dunno. In a decision as intractable as this, the status quo typically wins out, but is even that a good option? Guess what, dunno.