You have many ways you could do this, like by having callers hit a menu in UCCE that allows you to track them, to even something as simple as having the call come in and hit a script that simply sends the call to a label for that phone number where you're setting a call type.
A lot depends on how many of these you have, if you want to add UCCE into the mix/call flow of these calls, etc.
Many times, it is other factors as well (like should you/do you want to record these calls) that will drive the overall solution. A lot of customers want any interaction with an agent recorded/reported on/etc.