England have named a 16-man squad for the mini-tournament, which begins in Hobart on February 7.
As expected, it also contains Ben Stokes - although his participation remains unlikely while his wait continues to hear whether he will be charged with causing actual bodily harm in a fracas outside a Bristol nightclub on September 25.
Fast bowler Mark Wood and batsmen Sam Billings and James Vince are back in the reckoning in the sprint format, having missed England's last Twenty20 international against West Indies at Chester-le-Street four months ago.
It was initially anticipated Root would be due to have a short rest after leading England in the Ashes - set to end in Sydney on Monday - with the tourists battling to avoid a 4-0 series defeat.
He has been included, however, unlike all-rounder Mooen and wicketkeeper-batsman Bairstow, two other regulars across the formats, who like Root are part of the one-day international squad which will take on Australia in five matches this month.
Batsman Dawid Malan, another Ashes mainstay set to play in the ODIS as well, is also in the Twenty20 squad.
Chairman of selectors James Whitaker said: "Our aim is to become the best Twenty20 side in the world, and a strong performance in this series will give us the chance to progress up the team rankings.
"We felt it was important for Dawid Malan and Joe Root, who have had an intense period of Test cricket over the past few months, to play in the series and continue to develop their Twenty20 experience and skills."
There is once again speculation, meanwhile, that Stokes may be about to hear very soon whether the Crown Prosecution Service has advised police to charge or clear him.
In a brief statement accompanying confirmation of the Twenty20 squad, the England and Wales Cricket Board reiterated its current policy regarding the key all-rounder's selection.
It read: "Ben Stokes is included, though his involvement remains subject to any relevant legal or disciplinary developments in relation to the incident in Bristol in September.
"Should the ECB board receive formal confirmation that Stokes has either been charged or that he will face no charges, they would convene within 48 hours to make a decision on his availability for the team at that stage."
England T20 Tri-Series squad
EJG Morgan (Captain), SW Billings, JC Buttler (wkt), TK Curran, LA Dawson, AD Hales, CJ Jordan, DJ Malan, LE Plunkett, AU Rashid, JE Root, JJ Roy, BA Stokes, JM Vince, DJ Willey, MA Wood.
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