It was booming about 18 months ago.
While companies weren't calling the training providers, it wasn't far off that.
Yes, movement between companies is a lot easier. Especially if the one you're going for doesn't have a seniority list and you're already a captain on similar equipment.
T&Cs do move upwards a smidge*, but right now T&Cs are under threat and it really doesn't help current employees if folks offer to pay for training/line training.
*depending on where you are in the world and how much the airline is suffering from a lack of crew, the bonus/incentive to stay will be quite high. Note, it's rarely a significant increase to your salary. Often the company will put in a rider about it being payable in 2-3 years time if you stay. The company is of course hoping that there'll be a downturn and that offer will some how have to go to "save costs"...