After graduating in Economics from Queensland University, Lyn spent the first half of her career in the Prime Minister's Department in Canberra, specialising in micro economic and trade policy. A highlight was her deep involvement in advising on the major reforms to the Australian economy in the 1980s particularly with regard to transport, communications, industry and resources.

After a short stint in banking, Lyn returned to economic public policy, working primarily on issues of government administrative efficiency. She became executive Deputy Chair and then Acting Chair of the Australian Broadcasting Authority and led it into a merger with the telecommunications regulator. She chaired the new body (The Australian Communications and Media Authority) as a full time executive for its first 18 months until a long-term Chair was appointed.

Lyn later became the CEO of Australia's Antarctic program, which has responsibility for managing the logistics for, and operation of,Australia's four permanent stations in the Antarctic and sub Antarctic. Since retiring from executive positions in 2011, Lyn has served on not-for-profit boards in screen funding and land conservation and is a member of the Advisory Board of the Economics faculty of Queensland University. Lyn was appointed as a public member of the Press Council in August 2019.