It's been reported on the Dovetail Games support site that the Thomson/Oovee Class 150/2 pack will be withdrawn from sale at no later than 6pm (UK Time) today.
As this pack is integral to many scenarios from DPSimulation, along with undoubtedly hundreds around the community, I would strongly suggest any users that don't have it make a purchase if possible, especially as it is half price in the current sale.
The pack can be found via the Steam store by clicking here.