Apparently the use of a as in cat rather than ah (as in what you say to the doctor), specifically in imported words (like pasta and Mazda), is a typical Canadian English-ism. I read it somewhere when I was reading about Canadian English, I just don't remember where.

I personally tend to say Italian words with Italian pronunciation, even in an English sentence, because it just sounds wrong to me any other way. (This is because I speak Italian and lived in Italy for a couple of years when I was small and linguistically impressionable.) Therefore I say pasta as pah-sta, which most people around me don't.