Can you get carpal tunnel syndrome from typing on a touch screen / tablet? Or does touch reduce the chances of getting injured compared to a keyboard?

Depends. Actually, the primary cause for cts would be prolonged wrist flexion, such as sleeping with the hands tucked under the pillow or head when sleeping. Touch screens vs keyboards would follow the same logic depending on the prolonged posture. If the touch screen patient holds the tablet with a prolonged flexed wrist while typing with the other, they would more likely experience numbness than others.
Wrist position key. It's not the typing per se that gives you this condition, but the repetitive way you hold your hand and wrist. The nerve that gets pressured runs under the two tendons that pop out when you flex your wrist on the underneath side. So, bending your wrist down makes this area get pinched up. Try to keep your wrist relaxed and slightly more arched back when doing the same tasks over and over.
carpal tunnel synd. Carpal tunnel syndrome is compression of the median nerve in the wrist and it is exacerbated by a number of factors. These include repetitive motion, overhead activity or wrist flexion. Typically when using a touchscreen the hand is held elevated rather than in a neutral position. Elevation has been shown to be one of the exacerbating factors. Good ergonomics help minimize carpal tunnel syndr.
No. There is no evidence in the peer review literature that touch screen or tablet use causes carpal tunnel syndrome. If you feel you are developing carpal tunnel syndrome, i recommend evaluation by a health care professional to establish the diagnosis and the severity. Carpal tunnel can cause permanent changes in the median nerve if untreated for long.