Use of Apostrophe 's'

Is it correct to use the apostrophe 's' in the following phrases? Can it always be used for objects, place names instead of people?

- car's boot

- town's people

- London's train

-supermarket's trollies

Mister Micawber wrote:

No, the 's is almost exclusively reserved for human or near-human possessors.  Car boot, townspeople, London train, and supermarket trolleys/trollies-- none of these need to appear in a possessive structure, but if they did, they would most probably be the boot of the car, the people of the town, the train in London, and the trolleys from the supermarket.

That's a good reference but there is still one question left. I never got it when I have to put an apostrophe. I'm wondered if you could tell me the rule.

Mister Micawber wrote:

No, the 's is almost exclusively reserved for human or near-human possessors.  Car boot, townspeople, London train, and supermarket trolleys/trollies-- none of these need to appear in a possessive structure, but if they did, they would most probably be the boot of the car, the people of the town, the train in London, and the trolleys from the supermarket.

Umm, Hi,
I'm a little confused.
Isn't it possible to say "London's trains" instead of "London trains"? I think it's even better. I thought the possessive S could be used mainly for people, animals, and geographical nouns. The possessive S for inanimate objects is sometimes possible too (the table's leg).
In any case, there are no rules at all, but...

I think it's okay to use "table's leg" when you want to refer to that particular table.

Say you are at the furniture store. I say "Let's take this one." You say "Well, this table's leg is scratched. Maybe we can get a discount if we take the floor sample. Otherwise, we'll get one from stock."

CalifJim wrote:

the table leg / the leg of the table  the table's leg

LOL, I didn't choose that example at random, I once read it somewhere. I did a little search here, and find out it was GG who said that! Well, she also replied here, and her opinion is the same. I also read in some other forums about this question, and many native speakers agree that possessive S with inanimate objects is ok (Table's leg), although maybe not used much.
So it's really a matter of taste! I try to avoid those constructions, like you, I don't like them much, but as you see it seems others don't always find them too ...