You can see the new tooth design on the chainring here. Shimano is not using a narrow-wide design, rather they've gone with a tooth shape that provides chain retention using a modified shape. It has a very a subtle hook to trailing edge of the tooth. Lars is running a guide at the EWS, but Shimano claims the new teeth hold the chain on well.
Lars Sternberg is at the first round of the Enduro World Series and he's one of the first athletes equipped with the new 2015 Shimano XTR 11-speed drivetrain. No formal information on his setup was given, but he's running a single ring up front on the new XTR cranks, with the new rear derailleur, chain and 11-speed cassette which features 11-40t gearing. Until now there were a few production samples floating around Sea Otter, but this is the first we've seen the product in the dirt.
View Vital's 2015 Shimano XTR 11-speed First Look for all the details
PIT BITS - 2014 Enduro World Series 1, Chile