Surely if there are long stretches where the tram is not slowing for stops, it will be at a disadvantage compared to the faster top speed (but poorer acceleration) of a DMU like a 158 or 195 ?
The line is only 30mph until you reach the Cornbrook metrolink flyover. So its probably no faster than the tram lines on that section.
THe majority of the line appears to be 85mph, so a 60mph tram (ie a tram train) will have a significant speed disadvantage.
So if both the tram and train run completely non stop and have instantaneous acceleration - the tram will cover a kilometre in 44 seconds, whereas the train will take only 26 seconds.
So at most we are looking at 18 seconds per kilometre.
There are ~23 route kilometres between that flyover and Warrington Central, so we lose a maximum of about 6 minutes 12 seconds.
A tram/tram-train can easily have 11.7kW per tonne.
Even the 195 manages only ~8.8 and that is engine kilowatts and not motor kilowatts, so the disparity is larger.
Apparently starting acceleration on a Class 195 is 0.83m/s/s, whereas a tram train might manage ~1.1m/s/s. By the time you approach 50+mph your tram train will be accelerating
Also worth noting that the line is not all 85mph from Cornbrook to Warrington Central, at least one mile is done at 75mph between Padgate and Warrington, and there is a 65mph segment in the vicinity of Padgate (according to the sectional appendix).
That mile will lop at least six seconds off, and the acceleration and braking for that 60mph segment (which does not affect the tram/tram-train at all!) will hurt you further.
So you might lose a few minutes on the fastest train (probably less than 5) that runs non-stop, but your stopping trains will become drastically faster.
EDIT: The Down Line (in direction Warrington) has an extra nearly two miles of 75mph running that the Up Line does not, again near Padgate.
So that is going to hurt you a bit more.