It certainly is good news, and it adds to the of news that received little attention last year which is Nordens Level Crossing is to be replaced with a standard railway set up, all paid for by BP - whos tankers would have crossed the line at Norden to reach Wytch Farm (Wytch farm has since been sold by BP).
What i am however confused with, is as you say - what are the terms and conditions / what rolling stock are they going to use? Whilst there is a group working towards the restoration of a TC Set to use, and no doubt this'll be used with 33111, But this will probably require OTMR For the 33, and CDL for the TC Set. DMU Wise, they do have a 108, 117* & 121, and Dorset County Council did own at least 5 Class 117 Sets which were brought to work commuter services - However, these have all been sold on reccently, mostly for scrap.
So, i think this is going to be a case of wait and see then.
On a side note, the new signal box has opened at Corfe Castle now, and any communications between the Swanage & Network Rail, will actually lead to Basingstoke Box!
http://www.bbc.co.uk/news/uk-england-dorset-18117146
http://www.bbc.co.uk/news/uk-england-dorset-18100253
*Which is due to undergo a refurbishment soon.