This is likely only something that johnr can answer but I'll put it out there anyway.

I work in Mt. Wellington, Auckland. As soon as you step inside the building the signal drops to about one bar of 3G, then quickly drops to 2G. This happens across a range of phones, and stays that way until outside again. It had been like this for years which is why I changed to Telecom. Those on 2degrees lose signal strength a bit but by and large it remains on 3G.

With the cell site upgrades going on referring to better coverage and speeds, is it possible this problem might be fixed or improved?

I'd like to return to Vodafone but for me this issue is a deal breaker.