** Jefferies sees the recent speed boost by state-owned NBN Co to be a "churn event" for established telcos but a boon for challenger brands

** The speed upgrades from NBN aim to boost internet speed for eligible Fibre to the Premises and Hybrid Fibre Coaxial customers

** Jefferies sees TPG Telecom TPG.AX to be most exposed as 23% of its EBITDA is derived from fixed broadband compared with 4% for Telstra Group TLS.AX

** Adds TPG is more prone to potential competition from challenger brands, such as Aussie Broadband ABB.AX and Superloop SLC.AX, who have been taking share, helped by aggressive upgraded speed marketing

** Jefferies prefers Telstra and ABB, expecting TLS to benefit from a post-outage flight to quality after Optus' emergency calls failure last week, and ABB to gain from new contract with More Telecom and Tangerine Telecom

** YTD, TPG is up 12.2%, TLS up 21.4%, ABB up 54% and SLC up 46%

(Reporting by Anjali Singh in Bengaluru)

((anjali.singh2@thomsonreuters.com))