Codes do two functions...1.) grant access or 2.) grant access and track. You keep saying "track dept codes" which to me means you want to know how many prints are being done by each dept.
I may not be looking at this right but it seems to me that any tracking done by a phone installed app can only track prints made by that phone and the data is only accessible by the owner of that phone. In order to collect the data from 5 phones, you would have to querry the 5 users.
It only makes sense to me to have the access code in the app only grant access to the MFP. The MFP then actually trackes the number of prints done by each code.