"Big Dom" is another example of a modal progression that is non-diatonic but still has a tonal center, and there's actually a lot of music out there like this. Modality isn't just reserved for the diatonic chord progressions.
This progression consists of G7 - B7 - C7 - Bmi7 - Ami7, which is I7 - V7/VI - V7/bVII - III - II in Roman numerals. The secondary dominants in this progression are the B7 and C7, and even the I7 chord could be considered V7/IV. Regardless of the chordal movement, the progression resolves nicely to the G7 chord and therefore has a tonal center of G7. Improvise using G minor pentatonics, G Major pentatonics, and—for the really adept—arpeggiate the progression and outline each chord with its "sweet notes." For more on this, check out the Power Play series that I've put out with TrueFire.