The mobile network Three is sharing anonymous movement data of its customers with the Department of Health to monitor compliance with coronavirus restrictions.
It was revealed as part of a Staying Local Indicator bulletin by the Central Statistics Office (CSO).
It provides daily estimated percentages of county populations that have stayed within 10km of home, averaged over the preceding seven days.
It is based on statistical analysis of anonymised, aggregated, mobile phone activity records.
Newstalk's technology correspondent Jess Kelly told The Hard Shoulder mobile companies already have this data.
"The first thing to note about this information is that if you have a mobile phone and you a SIM card in that, your information is going to the network.
"Whether its Three, Vodafone, whoever you're with - that information is going.
"The aggregated data part means that they've pulled together information of Three Ireland customers, and they've anonymised it".
"It's been completely annoymised and that data then is being sent across".
She said this works as your mobile phone connects to the nearest mast.
"For example, my phone would say that I'm in Leopardstown cause I'm close to a Leopardstown mast - but if I go into Newstalk, it'll suddenly tell the network that I'm in Dublin 2.
"So that type of information associated with an individual's network profile can then be pulled together, all of the personal data is stripped away and then it's giving the CSO and the Department of Health a rough idea of who is going where, who's going beyond 5km and so on".
But Kelly says the data does not give insights into people's movements.
"It says, for example, that Mayo was the county with the lowest level of compliance at the time - around Christmas - but less than half the population stayed within 10km of home.
"But we don't know why people were on the move, we don't know if one or two of those people [or] maybe hundreds of those people had to travel beyond 10km whether it was to make an essential trip."
"So it's not an exact science, it's just part of the puzzle in terms of tracking people's movements".
While GDPR is not a concern, as Kelly explains.
"The answer is no - because there's no personalised data...it's fully annoymised information and it's being used for a specific purpose.
"The people handling the data have also said that there are specific parameters around how long it's being held and how it's being destroyed after the fact".
'No personal data'
The CSO says data from Three Ireland is "collated from anonymised data sets at a macro scale", aggregated at electoral division and provided to the Department of Health.
While the scope of the arrangement between Three Ireland and the Department of Health is "limited to informing the Government response to the COVID-19 pandemic only."
The data also feeds into a wider selection of data used as part of the COVID-19 response, with only "aggregated statistical data" provided - there is no personal data.
The CSO says it "receives and manages this data on behalf of the Department of Health."
"Only aggregate data is provided by Three Ireland, and at no time do either the Department of Health or the Central Statistics Office have access to personal data or individuals' movements.
"The outputs from this analysis provide important insights for decision makers and the public in the midst of a global pandemic", it adds.
Three has a 35% market share in Ireland and almost 2.4 million customers, as of August 2020.