I happened to discover that there are engineering works between Shrewsbury and Crewe on the weekend of 7th/8th Jan and Cardiff Central to Manchester Piccadilly trains via Shrewsbury and Crewe will be diverted. Does anyone know what route to expect?

Looking at the NRE journey planner, Saturday they are non-stop between Shrewsbury and Crewe and on Sunday they also call at Wrexham and Chester, so we know what route they take the Sunday, but not Saturday.
I've not looked any times up, but I'd guess the route for both days, judging by past diversions would be: Shrewsbury-Chirk-Wrexham-Chester-Crewe (reverse).That's strange, also according to NRE they are going via Chester on Sunday as Manchester-Llandudno services are being replaced by buses between Manchester and Chester.
I've not looked any times up, but I'd guess the route for both days, judging by past diversions would be: Shrewsbury-Chirk-Wrexham-Chester-Crewe (reverse).
Manchester to Llandudno services run via Warrington & Runcorn East.

Chrester to Manchester via Northwich. Some services at weekends are booked this route.Ah yes, I think Shrewsbury to Manchester services would double-back to Crewe after Chester. In fact that sounds correct as trains are still calling at Crewe, albeit nearly 90 minutes after calling at Shrewsbury.
Manchester-Llandudno services via Warrington and Newton-le-Willows are being replaced by buses between Manchester and Chester all weekend.
If anyone is travelling along these routes this weekend do pray tell what route trains are taking!![]()
Chrester to Manchester via Northwich. Some services at weekends are booked this route.
How is this possible though, because trains are still scheduled to call at Crewe?
Without looking at times or anything, maybe Chester-Crewe-Middlewich-Hale-Manchester?
Is this do-able?
Trains that travel via Northwich have nothing to do with the services that call at Crewe. They are 2 completely different services. The trains that run via Northwich on Sunday are North Wales Coast to Manchesters and the trains that call at Crewe are South Wales to Manchesters follwing earlier diversion after Shrewsbury either via Oxley Chord and Stafford or via Wrexham and Chester. Llandudno to Manchesters on Saturday would be bustitution as there would not be paths during daytime via Northwich. They would travel that route on Sunday but bustitution for stations via Warrington Bank Quay. The thread started re Shrewsbury and Crewe, but Chester to Manchester Engineering which is something completely different has crept in and apparently caused confusion.

http://www.networkrail.co.uk/browse documents/Rules Of The Route/Outrotr12/70lnw12.pdfBETWEEN 0035 SAT AND 1235 SAT, BETWEEN 0805 AND 1235 SUNDAY AND BETWEEN 1600 SUN AND 0400 MON:
TRAINS TO/FROM HEREFORD EITHER TO TERMINATE SHORT AT SHREWSBURY OR TO BE DIVERTED VIA OXLEY USING PLATFORM 3 ONLY AT SHREWSBURY AND THEN UNDER SINGLE LINE WORKING ARRANGEMENTS OVER DOWN MAIN BETWEEN PLATFORM 3 AT SHREWSBURY AND GOBOWEN. AT GOBOWEN, BACKSHUNT REQUIRED. TRAIN SERVICE TO BE RESTRICTED TO 1 TPH IN EACH DIRECTION.
RAIL REPLACEMENT ROAD SERVICE TO OPERATE BETWEEN SHREWSBURY AND CREWE. SERVICES TO/FROM THE TELFORD DIRECTION TO TERMINATE
IN PLATFORMS 5 AND 6 ONLY. FREIGHT SERVICES TO BE DIVERTED VIA STAFFORD, TELFORD AND SHREWSBURY AVOIDING LOOP OR TO BE DIVERTED
VIA WEST MIDLANDS, ABBOTSWOOD JN AND CHELTENHAM SPA.
BETWEEN 1235 SAT AND 0135 SUN AND BETWEEN 1235 SUN AND 1600 SUN:
TRAINS TO BE DIVERTED VIA WREXHAM OR VIA STAFFORD AND TELFORD UNDER NORMAL SIGNALLING WILL FULL USE OF PLATFORMS 3, 4, 5
AND 6 AT SHREWSBURY. RAIL REPLACEMENT ROAD SERVICE TO OPERATE BETWEEN CREWE AND SHREWSBURY.
BETWEEN 0035 SUN AND 0805 SUN:
ALL LINES BLOCKED
Enjoy working out what this means:
http://www.networkrail.co.uk/browse documents/Rules Of The Route/Outrotr12/70lnw12.pdf