That's going back a long time to when it was the 556. For its last 20 years it ran through Sowerby Bridge. One peak 556 in each direction continued for several years.
Much as I liked the 562, I was probably one of its most frequent users and I didn't cross the Pennines as often as weekly. I caught the 528 to Littleborough more often.
In 1993 I had a job in Chadderton and lived in Rippnden. For 10 weeks I got the 562 (or occasionally the 528) and then another bus. 4 days a week I was the only person on the bus in the morning with the same person every Wednesday. In the early evening there would be 4 or 5 people on the bus.
The Oldham to Sholver frequency has been cut to half its frequency since then. Odfham to Denshaw has been attached to another route, now. Halifax - Rishworth has gone from 3 buses an hour to 1 bus every other hour, with Rishworth having gained one bus a day to Huddersfield at times that work for college students.
I think the final straw was during the changeover to ENTCS when free local bus travel replaced various local schemes, ending the cheap agreement between West Yorkshire and Greater Manchester, so older passengers had to pay full fare. If it hadn't died then. off-peak travel on ENTCS would probably have picked up..
Thanks for the correction on the 556/Barkisland route, I understand now this was a much earlier 'edition' of the Oldham-Halifax service.
Sholver, with its huge housing estate(s), a lot of which still consists I believe of social housing, as well as Moorside/Watersheddings (very busy suburbs of Oldham) did benefit from a frequency of every 10 minutes or better to Oldham and Manchester on the 83 from its inception in 1993 - and even before then I believe the previous services 406(?) provided at least 4 buses an hour.
First Manchester did a lot of what they dubbed "tidying" (or similar) in 2019 which lead to a lot of routes split up in Oldham. 83 still provides high frequency Oldham-Manchester. New 82 from Sholver is every 15 minutes from what I remember. Whether residents of these areas think this is frequent enough I'm not sure. It's a very busy area in general that Ripponden Road.
Not familar with the term ENTCS but makes sense that it only aided the withdrawal of this service.
There have been a various amount of services and routes over the Pennines from Greater Manchester to West Yorkshire over the years, the only one in more recent times which appears to have retained a degree of success is the 184 service.