Hello Paul
With such a large driver pool that you have, without knowing the inside bits & pieces I would look at this as a 2 pronged problem.
1. You have until (with grandfather rights applied) 2014 to complete your training for all drivers.
2. How do we go about it?
In simple arithmetic terms, 2 drivers training a week for 5 years you will have solved your problem.
The cost: The cost will need to be covered in one of two ways.
1. Send the drivers on a training course for a week (costly).
2. Employ a trainer(s) for the specific job. Costly to start up, cheaper over the Long Haul (pardon the pun). Do your own in house training.
I would, subject to funding, prefer to do the training in house. The capital outlay in the setup would be high but the diminishing rule of costs would be applied over the term and would make it cheaper to operate than sending drivers for outside training.
I hope this cures your insomnia for this problem, I have looked in detail at this for over a year now and still cannot get anyone to give me a definative cost for the training.
Kind regards
Brian