Originally Posted by AndreyT

It is for so called "hybrid" braking systems, which are taking bicycling world by storm these days. They are hydraulic by nature, use hydraulic hoses, but at the same time run a steel cable inside the hose. Hydraulic fluid provides that modulation feel everyone is so fond of and lubricate the cable, while the cable helps the fluid to circulate and also provides redundancy in case of leak or rupture.

For obvious reasons, systems like this have regular inline adjusters, despite being marketed as hydraulic.