It is more then just track construction going on throughout the whole of George street with significant infrastructure and utilities renewal also taking place at the same time.
There shouldn't be any services to need renewing under the existing LR track. They could have inserted the points, frog and the H crossing relatively quickly and re-opened the line and dealt with the 'new' work on a more relaxed timetable without continuing to affect the existing line.
The current work down at Hay St seems to include not only alterations to drainage, but the alteration of a major looking gas main. However, both these items are NOT under the path of the existing track but off to the side.
In general, along George Street, the major pre-work is utility location, identification and in some cases relocation. From Park Street to towards the Quay, where they have been 'mucking about' for over a year now, the major work appears to the construction of two large underground chambers per block under the future path of the tracks. Having seen how these are located (right under the future track) and their size, I suspect these undertrack chambers will hold the control and switching equipment for the APS rail, each chamber supplying about half a block of APS.
Each APS segment is about 2 to 3 metres long and individually switched as the tram passes over it. That's a LOT of control and switchgear. Water ingress into the on track switches has been an issue in Bordeaux. The 'Tropicalization' APS probably meant the moving of these items from small boxed embedded in the road next to each segment to larger switch rooms that will be easier to keep dry.