1 Timid Slow Stubborn Carefree Creative Superficiality Tolerant Moody Crafty Dominant
2 Disciplined Conscientious Quirky Serious
3 Funny Happy Dynamic High Spirits

Yes, it works pretty good. The only limit is a connection range. So you can connect much more warehouses than you really need (in a free games I usually have 4-5 warehouses in each city).

But I found 1 issue in this system few days ago. If your warehouse connects both city and any farm - city will not grab that resource from warehouse. I hope its a bug. I've reported it yesterday but didnt recive an aswer yet.

Does that work?

I thought goods have to be delivered to a station.

Actually not. I'm connecting my warehouses directly to the city, and using stations for passengers only. So all of my fragile trains is actually moving to warehose only.

As I recall no payment is made for the delivery of goods to a warehouse. Unusually the purpose of a warehouse is to act as a common storage building where multiple goods can be delivered and then distributed as needed to various stations that demand them.

Does it means that guards will not add extra cost to goods in warehouse?

Personally, I would not give priority to employing security guards on passenger services or warehouse only delivery services unless their presence provided a boost to the performance of the entire train crew.

In fact, i didn't view train crews and a selection of individuals but as a team of individuals that had an overall performance. So, rather than asking 'should I add a guard to this warehouse or passenger train?', I would be saying 'Is that a better train to assign this train crew to?'

Perhaps if the crew works better with a security guard then they would be better off re-assigned to a train that wasn't just doing warehouse deliveries.

What about guards on trains marked "warehouse delivery only" ?
As I understand, I will get money for goods they delivered anyway. But will it be affected with guard?

- sorry for my mad english skills -

I agree with @Didz on security guards. Not a priority on passenger services (unless you're playing against a bandit-happy bot), but they can still trigger a significant boost to power or ticket price, especially on a true Express line.

I would not give a passenger service priority for a security guard. But nevertheless a security guard still provides a boost to other members of the crew even on a passenger service. So, they are not completely useless.