reception degraded after new Pitt Meadows Amazon warehouse construction

Firstly, how recently did this problem start? Is it just one phone or are there more devices / people / neighbours that are affected? Which specific make and model of phone do you have? There are multiple towers in the area. Depending on where you live in the neighborhood, one of the two shared towers may be closer to your location.

That Amazon warehouse has been there since mid 2021. The warehouse beside Amazon to the south has been there since mid 2022. The group of large warehouses between the airport and Harris Road have been there far longer. If you were getting service from the airport tower, I would have suspected you'd have started seeing issues as far back as 2017 when the first group of warehouses were constructed. Considering all of those warehouses are giant concrete and steel boxes that would easily block any cell signals. I suspect you were not getting a signal from the airport tower if the Amazon warehouse is directly between you and the airport.

There is one a distance to the west of the Amazon warehouse but it's located along the river beside the airport. None of the other providers have a tower at the airport. The one at the airport won't be very tall as a result of its location. There are two other taller towers along the CPKC Rail line. One at the Maple Meadows station and the other just off Harris Road and 122 Ave at the Fire Station, which is a block south of the Pitt Meadows station.

Freedom mobile and Rogers appear to be physically sharing the Telus tower off Harris Road. Freedom and Telus share the tower at Maple Meadows and Rogers has a tower right next to it. Bell uses Telus's network in many regions as a result of tower sharing agreements since Bell has few towers in western Canada. The map showing a Bell tower at Meadowtown Centre is really just the Bell store. Bell doesn't have an actual tower there.