How Flexible is a Service Really?

Today I did a short trip out to the North Station, the major transport hub for going from Amman to the north (Irbid, Ajloun, Jerash, and Salt among others). There are also services to the Balad, the Southern Station, and the King Hussein Bridge. The North Station, one of Amman's four major stations, is really orientated northwards, as opposed to Raghadan which has busses and service going everywhere.

Service to King Hussein Bridge

There was a very long line of unoccupied services with the yellow placard that mark them as allowed to go to the King Hussein Bridge. I can't imagine that they get a ton of use. There's also a Jett bus out to the bridge that's pretty easy and cheap to take. With this fleet of King Hussein Bridge service cabs, it seems like wasted resources to not let the drivers and their cars carry passengers to another destination if that day happens to be a slow day to the bridge.

This is part of a larger question I'm trying to figure out which is how flexible is the service system? What is specified? What is legally required? And in practice, how do drivers adapt? One the one hand, with just four people in the car, drivers can do a little more taxi-like customization of their routes and destination, especially if you're the last person left in the car. The pick up and drop off points do have defined signs like this one:

Balad Service Stop, complete with a sign marking which services wait there

and one driver told me that legally he can only pick up passengers at designated spots, like the one marked by the blue sign above. But he also said that if sees someone along his route who is trying to flag him down not at one of the designated signs, he'll look around for police, and if he doesn't find any, he'll happily pick up another rider.

Of course, without any regulation, service taxis would just be regular taxis, and I'm sure regular taxi drivers want to hold onto their monopoly of door-to-door customizable service. That explains why the services, depending on what neighborhood they serve, often have very defined roots painted on the side. It helps keep them fixed and more like busses than cabs. On the way back from the Balad today, I got in a service that said "Jabal Amman" to go to 1st Circle. The driver though pointed at the side of his car, where it says Jabal Amman in big letters, and then underneath it in smaller letters "3rd Circle", specifying where in Jabal Amman he can go.

I'd be interested to see who sets the routes and how they figure out how may of each service to allow. With the painted signs on the side, there isn't the flexibility that some of the bigger city busses have. With their digital signs, they can go from being Bus 442 to Bus 256 pretty easily if demand changes. The services are both more flexible in that they don't have their routes spelled out for them, and the driver can decide to change up his route slightly to accommodate one of the four passengers in the car. At the same time, it's interesting to see that there's someone, government or otherwise, who has gone through the trouble of partitioning an area as small as Jabal Amman into different districts, and assigning a specific number of services to each sector. That kind of central planning, the costs associated with it (like painting new specifications on the side of the car) would seem to be a bit less efficient than a freer service.