Shimano hydraulic disc brake lever and caliper compatibility My bike has Shimano BR M775 brake calipers and BL M775 brake levers.
The right lever for the rear brake has a broken screw in the reservoir, so it needs replacement.
As BL M775 is no longer available here, my second thought is to get the latest XT levers - M8000. 

However after I asked this question about Shimano brake hose compatibility 
 I realize that the newer models use a different type of brake hose (BH 90), with a narrow bore, as opposed to the older BH59 with wide bore.

What does this mean for compatibility - will "narrow bore" levers work properly with older "wide bore" calipers?
Ok, I upgraded and I might as well provide an answer for my question, in case anyone else is interested.

The bike is now sporting a BR M775 rear caliper, a BL T8000 brake lever (XT three finger model) and a BH90 narrow bore hose and everything works perfectly.
Putting the bits together was completely straight forward.