If you use Salesforce, you could work with your SFDC admin to create an activity type of "inbound call" that gets logged on lead activity history. This is probably also contingent on you having some sort of call tracking platform that is integrated with the CRM (something like a
NewVoiceMedia,
Connect&Sell or
PowerDialer).
Assuming you have that in place, you can then set up a trigger in Marketo that listens for Activity is Logged in the smart list and set the modifier to "is" or "contains" the name of the activity type that was created (i.e. "Inbound Call"). The flow could then be to add those leads to a list, send out an alert, etc.