Being a London bicycle commuter *and* a motorcyclist, I'm sympathetic to both sides of this issue, but, I've decided I do not support motorcycles or scooters in the curb lane under any circumstances.
Even in this land where so-called "filtereing" is encouraged, there is an important distinction to be drawn. Filtering is also referred to as lane-splitting, which clearly implies passing *between* cars (no around them on the curb side).
Anyone travelling in the curb-side "lane" is by definition at increased risk of being hit by turning traffic, and while bicycles typically must travel in this lane, we are also, typically, the slowest road users, and can be said to fit into a separate category. Motorized two-wheelers to not enjoy this distinction, and therefor are fools to occupy this space. And what's with the scooters who travel IN PARALEL to cars, riding along in the ditch and matching their speed? Who told them this was safe?
Some like to try to claim that that solid white line becomes dashed near the intersection to indicate that sharing the bicycle lane is okay at this point, but this is a self-serving and ignorant leap of logic to defy all.....well.....logic. No. That line becomes dashed to indicate that TURNING traffic is EXPECTED to move TO THE CURB (after yielding to any (bicycle) traffic in the curb lane) BEFORE executing A TURN! Except for bicycles, NO traffic should travel straight through the intersection from this location.
As for motorcycles/scooters in the ASLs, well now, lets chose our battles here. If they can get their in a safe and reasonable way, and don't block the curb-side portion (where most of the bicycles should be in any case, IMHO), then I'm okay with the practice.