Having looked at them I dont think the source is the Telephone Directory (or if so sampling is wrongly done which makes results totally worthless) nor do I think a sampled Electoral register non-Manx names are I think over-represented so I am a little mystified. As you can guess students who present me with data in this form are treated mercilessly!
Re Telephone Directory I have one but not that easy to go through (eg postcodes (derivable from address but not actually given in entry and dont actually correspond to any parish boundary that I can see) - the Kellys took about 10-20 mins to do - maybe 15 mins for each name (maybe some 80 common names in all would suffice) but to be honest as I dont think the info would be of benefit - post 1850 there has been much movement to towns esp Douglas. The 1881 census (I have an acadameic copy in a more readily searchable format than CD ROM tho no more info) is easy to set up to pull out this sort of info but obviously limited. Moore used a very subjective sampling of parish regs to derive his info - the IGI is not suitable (full of garbage)
I can see how the maps are automatically generated but I dont have the required graphical mapper program and to do by hand would be 10mins/map