I thought that the through services sometimes get re-routed through Manchester Victoria at weekends.
Diverting via Victoria doesn't always mean using the Denton line.
TPE▸ do divert via Victoria during engineering works but don't use the Denton line. I don't think the Denton line is even cleared for 185s and 170s.
The TPE services from the Leeds direction would take to Victoria would be the same as Northern Rail's Huddersfield-Victoria stopper. If it's an Airport service it would usually go to Salford, reverse, then go to the Airport via Piccadilly - which requires going through platforms 13 and 14 at Piccadilly. If it's a Liverpool service it would go via Newton-le-Willows to Liverpool.
EMT» and TPE services from the Sheffield direction would terminate short and have a replacement bus service.
Northern don't operate any services between Buxton/Hazel Grove and Preston/Blackpool on Sundays. The through service they do operate is a Chester-Stockport-Southport service, which during engineering works they terminate short and run replacement bus services.
However, if engineering works occur on a Saturday or Bank Holiday affecting Stockport-Deansgate then Northern will run the services between Buxton/Hazel Grove and Preston/Blackpool via the Denton line and Victoria.
The reason I said about it being unlikely that the Wigan-Buxton service would have used the Denton line is because it's either operated by a Picaddilly crew who don't sign the Denton line or there would be a crew change at Manchester Oxford Rd, so diverting via Victoria would cause crew problems, unless there was a spare crew at Victoria who sign both the Denton line and the Buxton line.
And a question about resilience, given the critical importance of those two platforms to the network in the North West.
To make matters worse long freight trains for Trafford Park have to pass through those two platforms.
GMPTE▸ converted the alternative route to Metrolink!
That's precisely why there are plans to have platform 15 and 16 at Piccadilly. Although, in a speech given in Leeds Ms Villers recently went in to detail about all the funding that had been spent on the rail - billions of it in London and then said the projects earmarked for the North will cost hundreds of millions, which we may not be able to find, meaning platforms 15 and 16 at Piccadilly may be at risk. Although, eletrification projects are safe.
