Is it something in B.C. water? air?
The “151” in the top line of the graphic, below, is the number of cases in which Clements v Clements, 2012 SCC 32, [2012] 2 SCR 181 has been cited, in reasons on CANLII, in court or tribunal reasons since Clements was released in mid-2012. It’s 151 times in total, 136 by courts and 15 by tribunals. To be more accurate, it should be 150 since the 151 includes Clements itself at the SCC
The 2nd number in the top line -49 – is the total number of court reasons only since January 2014. It’s 54 if one includes tribunals. The court distribution is: BC 36, AB 3, ON 7, NS 3.
CanLII – Clements cites numbers Aug 2014
The 4th Monkey Still in Abstenia 
There is a similar disparity regarding citing Athey v. Leonati. In addition, in Ontario, it is cited for the “thin skull” proposition, not for “material contribution”. Even the most recent B.C. case, Suedat v. Kara, 2014 BCSC 1837 (CanLII) still cites the material contribution.
Para. 67 of Suedat is problematic given the trial judge cited none of Ediger, Clements and Snell, and didn’t write that but-for means “necessary” or some equivalent phrase. It’s clear enough from that paragraph and predecessors that the judge was applying a but-for test so the question becomes what should he be understood to have meant. Failing that, it’s what did the physicians (whose evidence he accepted) say. This situation shouldn’t happen.
Not that I know of, but you’re right that most of the reported cases are mva decisions. However, what I did do is this search [“motor vehicle” negligence NOT “R. v.”] – without the outside square brackets – on CANLII, limiting the results to the last year. Ontario has 87 hits; BC 155 (as of 9:30 a.m. Pacific Daylight Time). Without opening enough of the hits to make sure the results are what they seem to mean, the gross numbers seem to support your thesis.
I suspect that the reason is that ICBC runs more trials than insurers in other provinces. Can you do a rough and ready estimate as to how many of those cases are MVAs?