Manchester Metrolink uses old BR track formation from a point between Cornbrook and Trafford Bar to Altrincham. ("Old" is the word for some of it - bullhead 60' jointed rail which has an interesting effect on the trams running at 50 mph). The NR line from Stockport to Chester joins at Deansgate Junction, south of Timperley, north of Navigation Road. The line through Navigation Road is twin track, Metrolink using one single line, NR the other.
The NR and Metrolink track single just north of Navigation Road, and both then double just south of Navigation Road. There are two level crossings, north and south of Navigation Road. NR Deansgate Junction box controls the two single track sections and the level crossings. The box presumably controls the Metrolink double track into Altrincham.
The trams and NR trains do not use the same track.
There is a double track crossover between the NR tracks and Metrolink a few yards north of Altrincham. The crossover is convential NR rail, without the height extensions on the check rails required for tram use, and is not, in any event, electrified.
The crossover is there to enable PW trains to move from NR to Metrolink should PW work be required on the old BR section to Trafford Bar. It does not look like it has been used for a while.
Metrolink has a central "turnback" siding south of Timperley, installed, apparently, so that Metrolink could terminate there were there problems on the NR section through Navigation Road and seems to be under the control of Metrolink rather than the NR Deansgate Junction box. The turnback siding is long enough to stable a number of trams, if required.
It is used quite regularly (as I can testify, after being turfed out at Timperley) when Metrolink goes pear-shaped, as happens equally regularly. I (so far) havn't seen it used for NR failures.
Metrolink can also reverse on the single track section at Navigation Road, and do that ocassionally when pear-shaped, presumably with the assistance of Deansgate Jcn box.
The NR line has an hourly service, Metrolink (usually) a 6 minute interval service. I wonder about the work requirements on the point motors and the level crossing barrier motors.
Some of that a bit off topic - the answer, though, is that there is a fixed link between the Metrolink line and NR just north of Altrincham.