Did you notice the change on the Deeprun Tram? Look again. The tunnel on the Ironforge side is the same, but Stormwind now has a ramp part. No, not a rampart. I mean it has those, but not as part of the tunnel to the tram.
What I'm saying is that as best as I can tell, the tram goes down, then up, ending at the same elevation as it started. Factor in the ramp and lack of ramp and bam, we know the exact relative elevations of Stormwind and Ironforge.
There is one problem: levelness. Since Azeroth is spherical, or close enough, some sort of rounded three-dimensional shape (based on evidence in Halls of Lightning), then level is a constantly changing meaning. Obviously the tram is not level at either entrance, or else it would be sticking out the world. It could be level at an exact distance between them, meaning that at either end the angle with the group would be the same. This would make elevation measurements possible and could be tested: measure the distance of the tram tunnel and if at the midpoint it is level, there you go.
But the tram exits are not titled. This leaves one last possibility: both ends are level. This is impossible with a straight line and a curved surface. A flat surface (flat Azeroth theory) has no evidence (then again, a round Azeroth has very little). But given a round Azeroth, the tram must be curved. Yet it appears straight. How can this be?
Obviously the tram isn't in the normal world in any usual sense. This explains the mystery of being tangential to the ground (parallel) at two points. And it explains why it goes through a large body of water when there is only dry land between the cities.
The tram is inter-dimensional and utterly nonsensical. This is perfectly consistent with gnomish construction.
And I have no clue of the relative elevations anymore. If we knew the curve we could figure it out, but how does one measure the extra-dimensional curving of something when inside the curved space? It would appear perfectly flat, as it does!
I may have just wasted your time. I'm sorry.