Wasn't the upgrade to HD supposed to happen last year, but got pushed back?
I recall comments along those lines: where it was believed that trails would switch to HD when trail production moved back in-house, from Red Bee. But trails remained in SD after that move. I believe that the existing playout contract stipulated that trails must be delivered in SD. That contract expires at the end of the year, so it's possible that trails could go HD in 2018.
I know that locally produced BBC NI trails have been in HD for some time. Presumably the same is the case for BBC Wales and BBC Scotland - can't recall?
All BBC NI locally produced trails have been made and transmitted in HD on BBC One NI for the past 5 years. Network trails remain upscaled from SD.
Bumper trails (made by programme production teams) e.g. Match of the Day, etc... are HD. These are either played out live from the programme gallery, or played down the line and lines recorded in HD for later TX.