This morning's commute and other commuting stories

Are they supposed to be putting salt down on the cycle superhighways?

Theoretically yes, but maintenance of cycle-specific facilities has always been a known problem. Carriageways are routinely 'swept' by car tyres less susceptible to punctures than bike tyres and don't tend to accumulate as much debris. Cycle-specific facilities are hard to deal with for road sweepers, for instance, if they get interrupted by constant bike traffic (the little vehicles they sometimes use are very slow, too), and here I imagine it will also be complicated by cycle 'superhighways' being along TfL routes and some kind of maintenance arrangement having to be worked out between them and the local council.

Another issue is that what can keep surfaces free of the ice that forms in very mild frost (not, of course, when it's really freezing) is the presence of underground services that are slightly warmer than the surrounding soil, and those tend to be located under the carriageway in this country, and not under the footway as in other countries, so if you stick cycle-specific facilities on the footway you tend to have that small additional difficulty.

Also, as London hasn't had much ice or snow for a couple of decades, most councils are not very well-prepared and it is hard for them to maintain a state of alert for the one or two days a year when you might get ice in the current climate, e.g. having a gritter that does nothing for most of the year and in the event will take more than a couple of hours to grit affected streets. I know of efforts to improve that, but in the current local authority funding situation, things like this just take a back seat.