WMT keep them separate? As the inheritors of the old “Central Trains random unit allocator” you must be joking!
They’ve managed to keep us couped up on a dogbox for years! Never a 170/172 ran down in error.
As far as I am aware, the plan is to introduce them by May 2019 timetable and replace the 153s. Then the timetable on the Nuneaton - Coventry and Coventry - Leamington will ramp up to 2tph on the Coventry - Nuneaton in Decemeber 2019. WMT are looking to get at least one ready for driver training within the month.
April is the target date for being in service on the Nuneaton/Leamington branch. Whether the direct service happens in May is another matter.
2tph assumes the bay platform at Coventry station is built by then, along with the old schenker siding in Cov Yard being ripped up and replaced with a plain line through to the bay platform, to avoid having to join the mainline into Coventry.
The second bit is unlikely to be done by December.