We only know about free previews when they get announced. We know Cottage Life and T+E are in free preview right now. Sportsnet and TSN will likely never be in free preview. They don't need to be. Nobody needs to be convinced to buy those if you're interested in them.
Telus previews frequently don't actually work for me (and this one doesn't for me either). I've never cared enough to pursue it, but if you do, try calling them. It's on the Telus site, so it definitely should be working.
They aren't on the Telus site, but I have a few channels in free preview right now:
313 Food Network Canada
616 Disney XD
700 National Geographic
701 Discovery Channel (ends Nov 30)
713 Love Nature
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