Alas, none were in service when I was there today! Even the staff training journeys were cancelled.
I checked on realtimetrains (RTT) before travelling and even whilst on my way to where I wanted to see the new train... it showed as being out and about but failed to turn up at the allotted time. I was at Kensal Green - just outside the station above where the main lines go into a tunnel, with the station platforms to my left.
The train I wanted to see was 5C29
https://www.realtimetrains.co.uk/train/F02338/2019/09/11/advanced due at 13:07; and again at about 13:39 on a northbound working.
Later in the day I saw that a train which had been out was terminated at Willesden Junction.
What did impress me however was that RTT showed every Bakerloo line train, using the code LT, as if London Transport was one of the many Train Operating Companies.