The proof of that is probably just looking at the 2011 and 2015 Election results; the latter was so bad that people had basically said that the Liberals were dead and very unlikely ever to form government again, when four years later they managed to get a comfortable majority government. Although "low floor, high ceiling" probably describes every Canadian political party, considering how unpredictable Canadian politics has a habit of being...
You also shouldn't confuse the Federal Liberals with some Provincial Liberal parties; they were basically the same for a long time but in recent years some provincial branches of the Liberals de-affiliated from the federal Liberal Party (who still stand for Federal elections in those provinces mind) and stand on very different policies: the BC Liberals are the main centre-right party there now; while the Quebec Liberals are... odd: its a broad-base Federalist party that somehow manages to have a broader base than the Federal Liberals (Tom Mulclair (current NDP leader) and Jean Charest (former Progressive Conservative leader, after he stood down from that he went into provincial politics and served as leader of the PLQ and Premier for a bunch of years) were both in it at the same time, which shows just how broad their base is) and its hard to place on the political spectrum because of that: I'd describe it as vaguely centre-right but I'm probably wrong. Basically Canadian politics is confusing and unpredictable, which means that its actually pretty interesting to keep an eye on.
The ideology of the PLQ is "whatever people funding it wants".
