2022 - Update 13:
The ALX400 types numbered 658 in Dublin's fleet (448 AVs, 200 AXs and 10 DTs), delivered from 2000 to 2006. These days their numbers are low, but they still hang on. Most routes have a general association with the ALX400 type, but some routes always look odd with an ALX allocation, the 83 and 123 instantly coming to mind. This has especially been the case for the 83 during its Harristown days, and the 123 for pretty much its entire existence except for the few weeks of the Special Olympics in 2003. But there is always the exception to the rule, with AXs having appeared a few times in the past week on the 123, though always very briefly (maybe a future week's update??) while the 83 can rely on a Euro duty.
In days gone past the ALX400 types would generally appear on the 83 as positioning runs in the morning and evening for Route 142. These days, the 83 has its own universal which can often have an AX allocated, at least in the evening time. The board is untimetabled, and often it does not appear on the RTPI screens, so you really have to be on the look out. Also, during the pandemic, with Harristown undergoing works, Broadstone were tasked with operating Covid extras on Route 83 during peak periods and I was delighted to catch AX582 so operating back in 2021.