You might want to take a look at using Splunk along with our CDR Reporting product running on Splunk -- "Cisco CDR Reporting and Analytics" ( https://sideviewapps.com/apps/cisco-cdr-reporting-and-analytics/ )
1) In that app the best way to solve this problem I think is to set up the apps "groups" lookup, at a minimum to manually edit that lookup such that each of the N numbers is in the lookup. (Normally you would set it up it pull *all* the information from AD for all extensions but it's easy enough to hand enter if it's a manageable number of extensions you care about. )
Then you can navigate to "Browse > Extensions", pick the group/subgroup for the extensions, and flip on the "show extensions with zero calls" for good measure. This will give you a report with call counts and durations in and out. You can also drill down on any row to get a full detail report about what the actual calls were there, and a cross link over to the app's general "Browse > Calls" UI for even fuller details about any of the calls across 200+ fields.
2) Another different but related direction is to create a report of all incoming calls grouped by what the initial dialed number actually was. This is easy enough - go to "Report > General Report", change "type" to just "incoming" and then change "over time" to "over initialCalledPartyNumber". Flip the tab from "Chart to Table" as well. Depending on various factors this might be a bit noisy, but it also might be pretty great. Hard to say.
Note that you can also use the "number" field here to enter all the numbers in question, comma-separted, and set the preceding pulldown to "calls to". That will cut down on rather a lot of the noise.
3) As a completely different direction, if the calls are going out through an MGCP gateway you can actually see which port, slot and subunit the calls are going out through. This is probably overkill here but... I thought I'd mention that too.
The app is available as a free 90 day trial as well, and only takes about 30 minutes to set up.
