I actually don't really watch it that often now but when I was living on the mainland and watched I thought the accents were often overdone but the expresses and ways of speaking were far more mainstream than you'd ever encounter in St. John's.
They'd have scenes where a drunken woman at a bar might say something like, "You looks some good tonight, my buddy!" with a super thick accent, and that's authentic enough, you could hear that any night out - but here you'd still be more likely to get less of an accent but a good, long rant with local expressions - something like, "Don't s'pose you wants to drag off, d'ya love? 'Cause buddy you're the gear. No need for to ask me to spread'em, wha, sure they're spring loaded. Come on now we goes."
Or maybe it's just George Street.
But, I'm exaggerating. In all honesty, though, they do mainstream it up a bit. I suppose they have to for it to be understood.
This is how the cast really sounds - it's not that different from the show. They just tone down the expressions and vulgarity for it:
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