The current situation is that, as noted above, GWR got the nod from the Department for Transport to bid for the paths needed for a two-houry frequency on weekdays and Saturdays.Nothing official, from what I’ve seen, other than GWR have applied to run the services on weekdays+Saturdays. Per my understanding, they’re meant to be 2-hourly, at least to begin with.
As mikestone1952 noticed upthread, RTT does now show ECS moves for this service, at either end of the route, but the actual journey isn’t (yet?) shown.
It’s been mentioned earlier on that this service depends on the introduction of Class 175s elsewhere on the GWR network, because that’s meant to free up some IETs. Don’t know if that’s still the case and/or whether that’s still delaying these Oxford-Bristol services’ introduction.
The application is with the ORR but its decision is still awaited.
Plus as many 175s as possible need to be in service and operating reliably by May in the South West, to release the IETs needed for this service to start then.
I guess that if that does not happen, a Bristol-Oxford start date may get pushed to September, to ensure the summer timetable is delivered in Devon and Cornwall and that Bristol-Oxford does not go off at half-cock, with multiple cancellations due to lack of IETs.