DWP changed their 0845 lines over to cheaper 0345 numbers on 17 March 2014.
Calls to 03 numbers are inclusive from landlines and mobiles else charged at geographic rate, exactly the same as calls to 01 and 02 numbers.
These are not premium rate numbers. There is no revenue sharing. The call price is set by the caller's landline or mobile provider.
The only profiteering is where a caller chooses an incorrect call plan or tariff for their needs, e.g. has the choice of unlimited calls on their landline to 01, 02 and 03 numbers for £8 per month but chooses to go on a tariff charging more than £6.50 per hour.
It is 084, 087 and 09 numbers that are premium rate. These are generally non-inclusive and cost a lot more to call than calls to ordinary 01, 02 and 03 numbers. Public services, customer services and financial services no longer use 084 or 087 numbers.
See a comparison of 03 and 084/087 call costs
http://www.fairtelecoms.org.uk/uploads/1/1/4/5/11456053/current_call_costs.pdf