Tim,
The 705-song database does actually include those songs that have not yet been found to have their earliest extant versions in commercial production and there are currently 86 of those. All of the 705 have been found in more than one version in English oral tradition between 1840 and 1940 (excluding Carpenter which was not available when the project started). I've just spent the past week analysing those 86 in terms of song types and motifs. What may be of interest, the biggest category was of songs that are of the catalogue type identified by Roger deV. Renwick.

I can easily send a copy of the presentation which describes how the project was put together and what it includes, to anyone who wants it. If I haven't already got it just PM me your email.