No projection until Labour Day weekend, but I've started playing around with the numbers a bit to get a feel for things.
What would the seat count look like if the Conservatives, NDP and Liberals all get 30% nationally? Obviously, it depends on how that vote is distributed. Under the assumption that the swings to get from the current vote support (polls from late July) to 30% are uniform nationally, I get about 125 seats for the Tories, 110 seats for the NDP, and 100 seats for the Liberals.
Under the same assumption, what levels of popular support would translate to a three-way tie? In my model, it looks like 32% Liberals, 31% NDP and 28% Conservatives.
Obviously, the above numbers imply that when the race is tight, the Tories' vote is the most efficient, and the Liberals' vote is the least efficient.
Now, what vote share does each party need in order to achieve a majority? To answer this question, one needs to make assumptions about where each party's extra support comes from. I will assume that for every 3% gained by the NDP/Liberals, 2% come from the Liberals/NDP and 1% from the Conservatives. And I will assume that Conservatives draw evenly from the Liberals and the NDP (counterintuitive perhaps, but "2nd choice" questions in polls do not suggest that Liberals are much more likely to defect to the CPC than New Democrats). Under these assumptions, the majority thresholds are around 38.5% for the Conservatives, 41.5% for the NDP, and 40% for the Liberals.
Once again, the Conservatives have the most efficient vote, but while the NDP's vote is more efficient than the Liberals' when support levels are similar, the Liberals would actually have an easier time than the NDP cobbling together a majority.