Try dougiemaclean.com or dunkeld.com, where you can order his two songbooks. They have all the chords and melody arranged for piano, but no information on tunings.

Quite a lot of the stuff can be done in standard EADGBE e.g. This love will carry in C, capoV, or Turning away in Em. I do Caledonia in drop D, capoIII, but it's not what Dougie uses.

Much of the rest of his stuff is in open Cm tuning (CGCEbGC). He does Ready for the Storm in this, capoIV. I use open Dm (DADFAD), capoII and it sounds the same.

I spoke to Dougie on his recent tour and the website will soon have tab on it.