In the end, 3/4 ridings were "holds" on Monday's by-elections, if you count Cumberland... as a hold. I'll go out on a limb and say that Montmagny... would also have been a hold given general election level turnout. Indeed, the Tories carried Roberval... by 27% in the 2007 by-election, only to win it by just 4% in the 2008 general election, while in the case of St-Hyacinthe..., they went from losing by 5% to 26%. While there was a large swing against the Tories in Québec between September 2007 and October 2008, it wasn't nearly as large as 21-23%. My guess is that relative to the Bloc, the Tories get a 5-10 point bump in rural Québec by-elections.
It's been two very quiet weeks on the polling front: only EKOS has put out new polls during this time! Here is the most recent one. The new aggregate projection is:
CON - 145
LIB - 75
BQ - 51
NDP - 37
This is the lowest that the Tories have been in the past 5 weeks, though the main beneficiary of this decline has been the NDP, whose popularity increased in BC and the Prairies, and not the Liberals, who are still mired at Dion levels. Counting both independents elected in 2008 as Conservatives (since they align themselves that way in the House of Commons), here are the changes since 2008 in terms of voting intentions and seats:
CON: -0.1%, 0 seat
LIB: +0.3%, -2 seats
BQ: -1.4% in Québec, +2 seats
NDP: -1.8%, 0 seat
The storyline: very, very little change. The Liberals are losing seats due to weakness in Atlantic Canada, while the Bloc is gaining seats due to the Tory vote becoming less efficient in Québec. Indeed, polls with a regional breakdown all suggest that Conservative support is less concentrated around Quebec City than in 2008, which helps the Bloc. The NDP and Conservatives trade seats in Ontario (Dippers down) and BC (Tories down).