At a LURS meeting when Croydon Tramlink was being planned I remember
the speaker saying that with the method of construction being used the
rails could be quickly replaced when necessary by simply cutting out
the polymer they are embedded in; I think he said it could be done
with a high-pressure water jet.

[...snip...]

You will find some expert and informed discussion about the works going on
and the whys and wherefores on the "croydontramlink" Yahoo! Group and I'd
highly recommend that to you.

My somewhat limited understanding of the situation is that there is a lot
more going on than just replacing the rails such as work on less than
satisfactory drainage channels. The need to replace the rails actually
seems to be a consequence of the method of construction. My inference,
which may or may not be correct, is that there is a body of opinion held by
many of those with expertise in the field that the contractors who built the
system were either lacking in knowledge of the tried and tested methods of
construction of tramways developed over many years and the reasons for them,
or they simply ignored them. Either way the end result wasn't impressive.