I seriously doubt the accuracy of this test. I am genetics major. A couple of years ago we could not even distinguish between wolf DNA and domestic dog DNA, much less between individual dog breeds. That was actually a big argument against outlawing wolf hybrids in some areas because there was NO way scientifically possible, either through DNA testing or by looking at a dog, to prove if a dog had any recent infusions of wolf blood or was a husky type of mix.
In order for us to be able to distinguish between different breeds, someone would have needed to find a distinct marker on the DNA of EACH individual breed. Because there are a lot of modern breeds (created in the last 200 years) that share common ancestry, or are composed of breeds still in existence, those breeds would share the same markers and you wouldn't be able to tell the difference between them.
A good example of this would be ACDs, made of dingo, collie, dalmation, etc.
Or Dobermans, made of (possibly) weimaraners, rottweilers, german pinschers, etc. There seems to be some debate about what exactly went into them, but all the ingredients bandied about are still breeds in existence today so they would share markers with those breeds, or possibly have lost markers in the mixing.
This is assuming that they managed to identify markers for all the foundation breeds in the first place.
I agree with everyone about the BSL. It is scary. Politicians are not scientists, and they are easily swayed by pseudo-scientific tests and studies. It's scary, and no one has any business knowing what my dog is, and telling me I can't keep her based on what her supposed ancestry is.