The most common response from readers is to blame "idiots" who managed the welding of all rail joints thus leaving no room for expansion.
The simple answer is welded rail is fine as long as concrete sleepers, metal rail clips to attach the rail to the sleepers and sufficient ballast is used.
To prevent a rail buckling an equal but opposite amount of "tie down" force needs to be applied, this is achieved by lots of good quality ballast, concrete sleepers and metal rail to sleeper clips.
SA WA QLD NT etc all have this kind of track and suffer little or no heat expansion problems at all in much longer bursts of hot weather than Melbourne.