Hell yeah!!! I use Blichmann burners under my 1/2 bbl keggles all the time. The way the Blichmann is designed, you simply place the retention pieces where you need for your kettle/keggle... It has no issue with the ~15" diameter of the keggles. Considering how Blichmann makes kettles that are far larger than keggles, it makes sense for their burners to be set so you can use a wide range of kettle diameters on them.
BTW, my keggle actually rests on the burner better than the 10 gallon BoilerMaker I have.