I emailed them a couple of days ago to ask the exact same question! They were very quick to send me a reply:
Sorry for the confusion on the web page.
To clarify the position of all trails at Mabie.
All walking trails are open although care is needed as there is still a lot of roadside timber.
The Green and Blue mountain bike trails are still closed.
The Red Phoenix trail is now fully open although a lot of care is needed as there is still a lot of timber lorries on the forest roads.
The Nith view walking trail and the Phoenix Mountain bike trail were just re-opened last Friday that is why they have not been updated on the web page yet, this should be sorted by the end of this week.
Neill Whitelaw Visitor Services Supervisor
It was the red trail that I enquired about, so good news for me! Not so good if you were after the blue or green.