^^^^^^^ Yeah, kind of scary the amount of force necessary to pull the toothed cable out, you'd swear something is going to break before it comes out (and probably does in some cases).
The cable appears to be Nylon or something similar. It is quite smooth and already has a certain amount of lubricity, so it should not be necessary to lubricate that part. The mast itself might benefit from a 'dry' lubricant or a light coat of silicone spray from time to time, but I think just keeping it clean is the better way to go. Definitely do NOT grease it, it will only gather dust and grit that way.
Over time... any exposed surfaces of the telescoping mast are going to begin to oxidize and accumulate road grime, so to me..it makes better sense to just clean the mast (restore clearances) than to try to lubricate it.