"The most interesting and sophisticated part is getting the right applications on the device. We have a strategy called Telco 50 - which means we think 50 applications are enough to manage all our functions."
Karonis said that the operator was now laptop-based everywhere apart from in the call centres, with hot-desking used at a ratio of around 10 desks for every eight users.
"Thin-clients only," he said. "With very little processing power, it's all dynamic computing.
"We're quite keen to work the way we sell. We're a top-class mobility company so we have to match that as an IT service internally, whatever the complexities of the merger. We have to step out of that and be compatible with the visions of the company to be mobile and forward-looking.
"We have done a lot of things to be modern, to make the way we work more collaborative."
Athens Airport and risk assessment
Ninety minutes into our time with Karonis on a Friday afternoon, I check with him that our discussion is not taking up too much of his day.
"But I'm only just getting started," he roars before enthusiastically discussing his role at Athens International Airport, where he also attributed his achievements to surrounding himself with a great team.
"I'm really interested in soft skills; not just the hardware," Karonis said. "The methodology of delivering is the vital part of the equation - how do you engage with marketing, with brand, with communications? It's all about modes of engagement.
"In Athens we applied the modern IT techniques of the way we build systems and the way we interact with users. We had to make sure we had enough testing time, especially with baggage handling which is one of the most complex systems you can work with.
"I took some big bets - and I'm probably one of the few CIOs who has survived an airport opening!
"The secret is to engage with all of your user community and to convince them. But engaging doesn't just mean listen because you end up being overflooded. It was about saying we needed to share things and have a common architecture and backbone.
"The keys to success was to pilot stuff very, very early. The big bang requires the appropriate planning, the appropriate mindset and the appropriate risk assessment."
Testing, stability and risk were constant themes for Karonis as he discussed his different roles and strategies towards various projects, and was of particular concern as he spoke about EE's product - its 4G network.
"4G is such an incredible evolution because I love the wireless world," he said.
"The foundation of our industry is the network, it's the product and our business is only as good as the network, and this is the one thing that permeates most into every area of the business.
Sign up for CIO Asia eNewsletters.