From the 4WD Systems Website about the Lokka
"LOKKA will perform the same as open and LSD differentials when the vehicle is driven under equal traction conditions, ie on road. The LOKKA allows the wheels to "differentiate" around the turn, but reverses the operation in that it transfers the engine torque (hence drive) to the inside wheel, rather than the outside wheel."
This sounds like it is not "locked" all the time. But reading further, they say it is.
It also explains normal open diff operation, but basically, a open diff "drives" the outside wheel. the Lokka Drives the inside wheel allowing the outside wheel to "overtake" the inside wheel in its operation. This form of operation causes the Lokka to "drive" the slower wheel.
and below is more on it operation.
"1. LOKKA has only 4 main parts - a pair of Cam and Axle (side) gears for each axle, there are some springs and pins, some have spacers.
2. LOKKA is normally in a fully locked state and only allows differential action by unlocking the unit when the ground driven force acting on a wheel (either during turning or when negotiating obstacles) forces that wheel to turn faster than the other driven wheel.
ie a turning vehicle's wheels actually travel two different paths with the inside wheel turning in one circle while the outside wheel travels in a larger circle, and therefore faster.
3. LOKKA makes use of two distinctly different sets of opposing forces that exist due to its design - one to dynamically couple the gears when engine torque is applied and the other to uncouple the gears when one wheel overruns.
3a. The locking force is applied by the action of the pinion cross shaft acting on a uniquely designed and shaped cam - the more torque that is applied the harder the unit locks.
3b. The unlocking action occurs due to the ramping effect between the low profile ramped teeth which force the cam away from the axle (side gear) eg when an outside wheel turns faster than than an inside wheel when cornering. Power continues to be applied to the inside axle. As the turn is completed and the wheels again rotate at the same speed, the outside lock re-engages.
4. It should be understood that only when there is an external force being applied to a wheel to make it turn faster than the rest of the drive train will LOKKA allow one wheel to differentiate. Slippery surfaces where one wheel would normally break traction in an open diff cause LOKKA to stay locked - even with one or both wheels in the air, LOKKA will remain locked."
What it basically says is that when the firm road causes the outside wheel to travel faster, the diff "unlocks" by riding up a ramp, but when a wheel has loose traction, torque is applied (from the engine) to a cam on the pinion gear shaft which increases it's locking.
So basically it's where the force comes from which determines if it's locked or not. Force applied from wheel - unlocks, force from engine - locks.
So getting to the point...
Lets say your gunning it along in some soft sand and the lokka is engaged, all is good. Then there is a big stump on one side of the track and you have to put a wheel on it, I imagine with an ARB locker you would turn the locker off just before you hit the stump to avoid excess strain on that CV as the tyre hooks into the rock. But with the lokka you can not manually turn it off.
In this situation does the Lokka disengage and allow differentiation or does it stay locked and you have to hope for the best with CVs?
I would say if you had to put a wheel up a stump, the lokka will stay locked, as you are driving it. As it is already locked there is no sudden locking force, but as you come down the other side, it is likely to unlock as there may be force from the wheel as the weight of the vehicle would cause it to go faster. Either way, if one wheel is forced by the "terrain" to travel faster, it would unlock, but as soon as the other wheel speed catches up, it would relock.
I would not see too much problem with this system in the situation you suggest.
This is the website I got the info from.
4WD Systems | LOKKA Differential Locker | Gear to Goannawhere