No, I do not have numbers as to when those defences were used.
The Canadian Centre for Justice Statistics only gets raw numbers, acquittals and such. The 84% is up from what it was at one stage. It was about 70%, 15 years ago or thereabouts. I think you'll find that number in the 2002 Juristat on impaired driving. It was 72%, so some of the changes have been helpful.
The proposals are in fact to respond somewhat to criticism in the St-Onge decision that Parliament had never specified in detail the conditions that the alcohol test committee considered to be required. The alcohol test committee has clarified its position in several ways since that time, and the bill actually says that if you follow what the alcohol test committee did, there is conclusive proof that it was right.