It replaces the Liverpool-Manchester local that no longer runs beyond Warrington Central. (The Northern service to the Airport hasn't run since the pandemic *). It's in that path, but calls at Irlam and Urmston to replace the local - and the time that takes means there isn't time to call at Warrington West (except on Sunday when it doesn't call at Irlam and Urmston).
* This was supposed to be a flagship service for Northern (old regime). That included the daft idea of saving 4 minutes in its times by making the local leave Lime St first, cross SL at Wavertree Jn, get overtaken by the Airport train, then cross back at South Parkway (adding 8 mins to the local's time, and crossing the Down Fast twice).
Supposedly reversing the Cleethorpes-Airport trains at Piccadilly was "operationally difficult", one reason given for extended them to Liverpool, but if they regularly curtail them at Manchester, they'll occupy a platform for an hour (though yesterday one of the westbound services with TC difficulties that meant it couldn't go beyond Piccadilly turned round in 5 mins and went back to Cleethorpes).
I hope they've dropped the idea of TPE taking over the Liverpool-Nottingham route leaving EMR with just Nottingham-Norwich.
It may have a revised stopping pattern to compensate for the inappropriate truncation of the stopping service at Warrington Central, but it is a direct replacement for the Northern Airport service. It initially survived the pandemic. I used it on 16 September 2021 as far as East Didsbury, as well as other occasions, probably knowing it would be withdrawn within weeks, but I found it full and standing with a 6 car 195s and recall overtaking a 156 somewhere between Mossley Hill and West Allerton.
There’s a lot wrong with those slow lines in:
1. Why they have survived in the first place but remain virtually unused,
2. Why there is not a 4 track junction onto them at Edge Hill,
3. Why Wavertree and Sefton Park stations have not survived when sufficient capacity to serve them exists on the slow lines,
4. Why only the fast lines have access to the Allerton curve, requiring slow CLC services calling at Mossley Hill and West Allerton to block the fast lines and
5. Why they run on the east/north side of the formation necessitating a flyover when the Runcorn Bridge diverges to the south and the fast lines into Lime Street are on the south side of the formation.
I will note that if Monday’s 12:19 service had overtaken the train in front, it would not have reached Castlefield 16 minutes late. The reason/excuse I have seen given for not reversing anything at Piccadilly is that it takes up 2 paths for the price of 1, despite the fact that there may not be enough platforms to run an additional train and that reversing at Piccadilly is not as capacity compromising as crossing the throat to reach Guide Bridge from Castlefield, reversing at Oxford Road or attempting to traverse the Ordsall Chord.
That said, Lime Street - Cleethorpes removes 2tph from the already saturated Styal line, doubles the frequency (and more than doubles the capacity) between Lime Street/Warrington Central and Stockport/Sheffield and frees up 195s for other services in favour of underutilised 185s. I would argue that it would be more sensible for Greater Anglia to take over the Nottingham - Norwich portion of the EMR service than for TPE to take the Lime Street - Nottingham.