There is as much evidence as there is controversy as to whether 'A Few Old Tunes' (as well as the two other known volumes in the 'Old Tunes' series) is to be considered a legitimate BoC release or not - On the one hand we have samples contained within these tracks (as well as entire tracks) that would appear on subsequent releases in a different form. There is a pervading aesthetic to these tracks that is strikingly familiar and teleologically cogent with the known BoC discography that would follow.
On the other hand we have the fact that Mike, Marcus and the labels that harbour them have never mentioned this release or backed it's authenticity.

The general concensus among the BoC fanbase is that 'AFOT' is, indeed, authentic. There are just too many common samples and some of these unreleased tracks have popped up in some odd places; '5.9.78', for instance, appeared in a Nissan advert directed by Chris Cunningham. As well, 'P.C.' appeared in the online trailer for the BoC EP 'Trans Canada Highway'. The apparent outright usage of these tracks pretty much solidifies the authenticity of 'AFOT' for many people.

Presumably the 'Old Tunes' series of DIY cassette releases were compiled to be given out to friends, family and possibly small labels as a demo of sorts. As BoC gained in popularity it was inevitable that these old rarities would leak into the lawless realm of the Internet as low-quality mp3s.

There was one well-documented incident of these cassettes appearing for auction on eBay (with a starting bid placed at over $900 USD). The auction was quickly removed; presumably BoC or other Hexagon Sun members had some part in it's removal.

The bottom line is that if you want to hear this album, or any of the three 'Old Tunes' volumes for that matter, you're going to have to download it from P2P file sharers. Unless it were someday officially repressed, expecting to acquire a physical copy of these cassettes is a fool's errand.