They are both primaried with their house strain and barrel aged with brett brux. There's an interview someone from Goose Island did at some beer fest a couple months ago, I'll post it when I get home. -edit- Gabe posted the link above.
Alternatively, they have recently released Matilda Lambicus done with brett L.
Juliet is my favorite of the sisters, but to be honest anything out of their barrel program has been outstanding.