If a journey I’m looking at for Saturday evening is showing as running, no engineering works or replacement bus services, can I reasonably* assume that it will run as planned, on rails, in a train?

*and yes, I know my definition of reasonable and Northern trains definition may differ.

See if you can find any services that are cancelled. If you can then there is a reasonable chance the service is running. if you can’t find any cancellations then you can assume the website isn’t showing them and your train may well be stuffed.

Where from / to?
Some services are more likely to see cancellations than others…

It’s not unheard of for a service to show as on-time right up until you’re standing on the platform with 3 minutes until it’s due then it’ll show as cancelled….

Where from / to?

Sandbach <-> Alderley Edge

Your best bet is http://www.journeycheck.com/northern

That gives live service updates, cancellations, short-form notifications etc.

Also useful to check Real Time Trains. You can find a specific train and check if running and on time at the previous stations.
https://www.realtimetrains.co.uk/

I’ve found NRE reliable in the past and indeed this very morning.

Fatality on my line, so went back home. Checked NRE and the next train that was showing not cancelled came in

Good luck