I mean I'm just working with the data as presented. We can and should look for confounding influences - hence why reproducability is so important. However a mean 2.7x rate increase is not trivial if we start thinking about possible epidemiological impacts.
Based on the evidence available right now, I don't think there's a link between cellular technology and cancer. If there was about one more study like this one -- from an overall reputable research outfit, with a good population size -- I'd start to reconsider.
And if another study is done and doesn't find the same effects, then that's still another interesting case of the decline effect. So, either way, it's a win.
If anything this warrants replication.