What I've done is that I've only looked on matches where the losing team was completely wiped out and where no one had disconnected so that the mech name or status was hidden. Other than removing a few such matches these are 100 straight matches, I can provde the screenshots if anyone would like them for "proof" that I haven't just made up the numbers.
Now what I've collected is the number of Clan vs IS mechs in each team and also how many Clan mechs and IS mechs that survived the match (obviously only winning team).
I know it's just 100 matches, but that's all I had the energy to go through and collect numbers from...
Anyway, this is the result:

But what we can see here is that the winning team have a higher average count of Clan mechs than the losing team and in 55% of the matches, the team with most Clan mechs win.
I'm not really a statistics guy so I'm hoping that someone that is can take the numbers and get some more interesting info out of it.
Here is the spreadsheet if you would like the copy the numbers.
Oh yeah, almost forgot, Clans now proven OP easy mode!
























