Only if you expand the bore from the same point all the way through.
If you expand it downwards at the stations, and upwards away from
them, the incline is significantly reduced.

And if you did that with steep enough gradients, you'd need EXTRA
powerful motors on lots of wheels for each and every train to escape
from the holes you've dug.
WHEREAS
If you make the line go up into the stations and down out of them, you
don't need to use the brakes and a quick push from the guard, sets the
train off and up to running speed as it accelerates away down the slope.

Jim