I am not quite certain about what you want to get resolved here, but I'll try to the best of my ability to understand and provide you an overview of what it is you are doing wrong and what you have to do to get this to work properly.
Firstly, you mention each bus docks back to the network after a period of X min/hours away and during that time, I assume they sync from the network.
Secondly, you mention you created local "shares" that are spawned by a local administrator on the local computer.
Thirdly, your thin clients can connect to the computer (locally, I assume) whilst it's off the network.
So. I have deduced that you have only local computers, not domain computers and no domain servers.
You have two options here:
1) You can create a domain controller/FQDN that will house DFS shares for each bus. You can then control the information centrally and enable offline files for DFS. This will permit the servers on each bus to retain the data and provided you enable the ability in the forest's group policy, you can push it to the clients.
2) You don't install a domain but leave the share as it is. You mention that while off the network, no logon service is available, that is because however you are connecting, the client cannot see the logon server anymore. A simple reboot and direct connection to the bus server will fix this. (My previous SF answer sheds more light on this: nas - Synology and Active Directory.
2.1) If you wish to connect your thin client directly to the server without passing through a switch/hub, then you will need a crossover [Wikipedia] Ethernet Crossover or a NIC that allows for Auto-MDIX (senses whether the connection comes from a like device or non-like device): Medium Dependent Interface (MDI)
Your problem can be fixed by following the "nas - Synology and Active Directory" post I submitted. Just make sure that you either have DHCP running on that server to give the thin client an address, or static address on the same subnet and address range.
I hope it helps. :) It's a common problem within Windows whereby the "location" of the server is gone. You just need to fine tune it to handle disconnects for X min/hours and then when the bus docks back, it syncs and connects/your thin clients need to be constantly connected to the server.
Remember your thin clients are logging into the server hence the logon server issue.
EDIT: Forgot to mention that if you have a pre-existing domain and the AD DS is not on the remote roaming servers, you won't be able to login unless it's cached on the client. From there, use the FQDN\username and log in, just make sure that the share is located on the bus server and is accessible from the roaming network (see subnet requirements above)