I'm wondering if CZ is to get subsidized landing fees in HEL by Finnavia? Would make a great case to forfeit AY metal and share the gains from cheaper flights!
As for connections:
Midnight departure from HEL would put the route on par with HKG route, which currently is the main option for HEL-ANZ. It would be interesting if one could find slots offering a different schedule via CAN, but I do see the problem.
Now, the CZ way of handling bad connections is just to put people in hotels for free. I've enjoyed some nice STPC with them on onvernight connections. Probably not a service Finnair will foot the bill for, but for a CZ coded flight with overnight international connection in CAN there will be a 5* room waiting for you.
Same will probably go for a CZ customer coming from domestic and connecting to CZ/AY to HEL, so overnight connection on that end may actually not be that big of a problem.