Much of them use adapters such as the Letus (http://www.letusdirect.com/cart/letus35-ultimate.html), Brevis from Cinevate (http://www.cinevate.com/catalog/) and Redrock (http://www.redrockmicro.com/micro35.html). This optical devices combined with prime lens (fixed lens) allow to obtain shallow depth of field working with big apertures. Lighting is crucial because they tend to cut some f-stops in exposition.
DSLRs offer great image, but in television shows that require professional audio recording I haven’t personally seen a whole production filmed with them. Music videos and short productions are another matter.
Hope this help.
