Not sure if this answer is what you look for but I think it can not be done without 3rd party software. I will explain with a scenario to see if this is what you look for.
We have a customer using RFID tokens to enter the building but also login at PC's. If they walk away the PC will auto lock etc.
When they put down the token, it will auto login their desktop with their profile, as well as phone and UCA.
You need 3rd party software to auto login the phone to that user's suername. Also you need 3rd party software to script UCA auto login. But from what I heard the UCA is a bit tricky since the 3rd party software will have to identify/capture the different overlayed screens UCA uses in order to login correctly or at least thats what they told me but it can be done.
The whole script logins the Hotdesker first and then it logs in the UCA since UCA prefers the default device to be active and it avoids confusion for the user.
Logging out people is easy though since it can be scheduled.