Well in this quote from the DOI from June 2019
A spokesman for the Department of Infrastructure said: ’The tram tracks are 300mm wider at the request of Isle of Man Transport, the position of the tracks is virtually as it was before.
’The roadway is 3.25 metres wide on either side of tracks as a "running lane", allowing 1.8 metres for parked vehicles. The carriageway is now a consistent 3.25m width along the route - previously it was as narrow as 2.8m in places.
’There shouldn’t be a need for vehicles to move onto the red (sienna) tram corridor.’
So they clearly feel no need to follow their own manual