Tyler was formerly the group managing director of Telstra Business. He has 25 years experience in ICT across Europe, the Asia-Pacific and Australia/New Zealand.
NBN Co chief executive Bill Morrow, said: "NBN Co has benefited greatly from John’s leadership and many contributions over a five-year tenure. Over the last seven months, John has built a dedicated business segment team that Paul will now lead to take us to the next level.
“Paul is a high calibre executive with significant experience and a proven track record. I'm delighted to have him as part of our team and look forward to seeing him drive significant momentum in this vital part of our business.”
She has been with NBN Co since June 2014 and will be with the company until mid-August when its full-year results are due.
Morrow said: “Karina has led us through countless press briefings, senate hearings, community engagements and employee activities in arguably one of the hardest communications and government relations roles in the country.
“While we are sorry to lose her, Karina leaves us with a strong team who will continue to report on our progress, clarify the facts, and help manage the reputation of the company.”