They probably used the Yealink's built in Hot Desking method, which isn't the best really as it requires giving the SIP credentials to the end users. You can mitigate these issues with a Trusted ACL/VPN/Local Network only... but it just gives me the ick knowing the password for the account will sometimes end up being 1234 at the request of someone.
If not, they are probably only merging the credentials part of the config which increases complexity quite a bit and may come with limitations like 'everyone must use same settings for handset volume' or something like that which needs a reboot.
Or it might just be one of those old digital phone systems like an Avaya IP Office.
Naw they aren’t using yealinks hot desk feature as that IMHO is very insecure. Like I mentioned above, I believe you can kinda do this right now in fusion....
According to one of my techs
If I were login to a phone (*11) and let the provision and reboot. You go to WebUI look at devices and you now see that device has its' alternate login now. You then take that phone offline, hold "OK" factory reset it and wipe it completely out. Then plug that phone back into the network... you can simply provision that phone and it will provision as the "Alternate" user without rebooting at all. So, I believe this can be done
The other company that was doing this was using Bicomm which is asterix i believe.
i personally have not deep dived into this but it makes sense to me logically why this should be simple to do. I mean honestly it is no diff then provisioning the phone. Without hot desking, if a customer called me up and said user david and john have swapped seats can you update their phones, I would simple go to their extension remove and swap their devices, go to their devices and click provision and it would work just fine, without the need to reboot anything. so... I dunno seems like this should be easy to do.