Hello RexyTheDog
I will try to help you with the information I have.
Let's assume you are playing on one of the Desert BTPro servers as you said,
If the centre square of the town is in the desert, at least 1t of food and 1,000L of water per month must be delivered for the town to grow. The town information window will show whether food and water was delivered recently.
The towns will grow very slowly on their own, so in the case of small towns not large enough to accept food, it is simply a case of waiting for them to grow. As with any other cargo a station needs at least 8/8 of food acceptance in its coverage area before it accepts food.
Water must be delivered to a Water Tower industry. Water Towers may be generated automatically in towns, or a player may choose to fund one using the "Fund new industry" menu.
The amount of excessive food and water delivered has no effect on the rate of town growth.
If the centre square is not in the desert, food and water are not required for growth, although Water Towers may still exist in the town and food/water will be accepted.
about grwoing a CITY. the problem is all of the resaults are about TOWNS and not CITIES...
A city is a special form of town that will grow twice as fast as a regular town. A city is also larger to begin with.
If it is possible, I would recommend you to install the BTPro client version so you can see more detailed town growth speed on every town's information window, use the automatic regularly advertise or funding, and you could play any normal multiplayer too (not only BTPro servers).
Try server #15, if you saw me I would really happy to help on CB related stuff.
Hope it helps and see you around