For any tunnels in the garden my personal suggestion would be to lay the track and then place bricks either side to a height above your wire height and then lay concrete slabs on top, then you could put any soil on top of that for planting.
The gradients are obviously not so much of an issue where trams are concerned - as in the 1:1 world - because there is much less load involved.
In Montreal, they ran trams on slopes that were steep even for cars. I believe it got a bit dodgy on winter ice.The gradients are obviously not so much of an issue where trams are concerned - as in the 1:1 world - because there is much less load involved.
The gradients on some of the London tram tunnels far exceeded railway gradients
I presume you mean to creat a tram rail effect. Did it many years ago with a short section on my old line in Luton. Had to do a job for the neighbour some 10 or more years after I had put the track down in the concrete and In spite of many changes in my old garden that bit of concreted in Track was still present as good as the day it had been laid. What I had done was to lay the track on a base of concrete and do the tram track effect at the same time with the same batch of concrete thus the complete lot was a good solid lot probably 2-3 inches deep.
I have been looking at tram vids on Youtube, and whatever scale they are in, the building detail usually seems to a very high standard. The buildings aren't just added on to fill in gaps they are a major feature, unlike some rail layouts with "token" buildings. Both approaches are fine, and it all depends on personal preference what buildings and how many you have, but I do like the atmosphere the tram layouts create, almost as good as a trip to Crich!
If you look carefully at that bogie tram it is a cut and paste of possibly 2 LGB Trams which would make a slightly longer one thus having bogies would make an interesting variation.
