I know that in Russia the telcos were able to grab the spectrum at almost zero cost. Bad for the state budget, great for telco market cap, but looks like it's also good for consumers.
- Polish people are tech savvy and get easily excited about new tech, so there's high demand for data services
- there is a lot of competition. There are four major vendors, and there's already more than one mobile phone per citizen (and that's including infants). So the only way of acquiring new customers is to make them switch from other telecom.
- Poland is pretty small and have relatively high population density, so it's pretty easy to have good coverage.
- It is easy to avoid taxes (and even if you pay them, they are pretty low), so telecoms have a lot of spare cash to invest in the infrastructure :)
In the U.S. there are multiple competing carries of meaningful scale but the data plans tend to be expensive.