Perhaps it takes someone who has a strong and developed musical personality. In fact, a musician has to be convinced that what they are doing is the most important thing... the belief has to be practically religious if there is any hope of persuading anyone else! While being fully grounded in ones own direction, such an all-round musician must be, well... well-rounded. Curiosity in music that will broaden his/her horizon and therefore become a deeper, better musician is key. It is the balance between sticking to ones own direction and being open to the path of others that makes such a strong person, human being and musician.
Well in the case of The Band of Joy, such a musician might be Buddy Miller. The project was pretty much under his direction, and it is his strength as a musician and musical visionary that has some of the best talents in the business trust in him. He holds the title of instrumentalist of the year by the American Music Association and seems to be involved in all things Americana.
Many folks have been more and more interested in such cross genre explorations... and the blend of blues, country and jazz is gaining momentum!