In general, they're always manned. If not, I usually find that there's a staff member floating around somewhere. At Dundee, for example, I had to ask the dispatcher because no-one was there!
First Scotrail tend to man these barriers when trains are due which, although isn't the ideal situation, does let you thorugh (eventually).
That wasn't the case at Aberdeen last week. I got off a train from Dyce on the far platforms, and there was no staff on the barriers, or indeed that platform! Luckily, I had normal a 'point to point' ticket, which work thru' the barriers. A few weeks before that, I'd been on an All Line Rover (which don't work thru' any barriers), so, hypothetically, I may have struggled to make a tight connection. I was always under the impression that if there isn't enough staff to man barriers, they must be left open (and it states this in the Northern Rail guide on how to use their barriers).
Thank's for that, you've put my mind at rest. I travel on the trains relatively often and have never seen anyone use anything but the standard orange tickets. My main worries were getting through ticket barriers and why I only had one ticket when I had to change at birmingham and haymarket. The ticket barriers are usually always manned during the day time aren't they? I don't want to be rushing about trying to find someone while my trains about to leave.
They are actually quite common, If you use 'Intercity' services, there are generally a fair few pax with them, however, if your more used to regional trains, then orange tickets are the norm.
Also, when you are issued with the large (ATB Elgar) tickets, you should be issued with a gate pass- that is credit card sized, and fits thru' the barriers, however these only seem to be issued for tickets '+ London', the issuing system seems to assume that National Rail stations outside London do not have barriers (or that they will always be manned). It would be sensible if there was a 'gate pass' issued as standard with Elgar tickets, especially if you are booked to travel from or to a barriered station.
Of note, the large tickets (RSP 3597 /8597 equivalent) are very common throughout Europe, and are used in Ticket Vending Machines for Eurostar and also at SNCF stations in France.