Cell phone providers and credit history

HS had an article on how the cell phone providers demand security deposits from foreigners, and Finns without a credit history.

According to the article, DNA, Elisa ja Saunalahti demand a security deposit for a year.

Funny. I've had GSM service from Sonera, Elisa (then Radiolinja) and DNA, and none of them asked for any deposits. Some other people say they were asked for a deposit. The thing seems to be quite random.

But the really funny thing about their "credit history" claim is that there is in fact no credit history in Finland, certainly not in the sense that they mean. Not a positive credit history, at least not officially. A credit history in Finland only contains the problems. If there have been no problems, it says that there have been no problems. It doesn't say "has had a credit card for 10 years", or "took out a car loan 5 years ago, has paid it back already", or "has a mortgage and has been paying it on time". The Finnish credit history doesn't really make any difference between a person who has just arrived and the person with a 30-year history of taking out big loans and paying them back on time. It just says "no problems".

And as to Finns that have just moved back to Finland: how do the cell phone providers even know that? The population register does not give out the info on the person's previous addresses; and DNA, Elisa ja Saunalahti are not even on the list of companies that get their customers' current addresses from there.

So, are they lying, or are they getting their info somewhere they shouldn't be?