As discussed with a lot of my customers Exchange UM no longer uses System Center (SCOM). Exchange 2010 with SP1 now has built-in reporting.
Call Data Records (CDR) are generated after each call. The server collects audio quality metrics with the same metrics that are used for the Monitoring server for Lync. Once the audio metrics are received they are stored in the e-discovery mailbox. They also have a lifetime of 90 days at which time they are automatically erased. This value can’t be changed but if you need them longer your can simply import them into a CSV file.
UM reporting features are done via EMC toolbox. If you are a tenant UM Admin you can also see them in ECP.
Call statistics provide stats about calls received or sent by UM Servers. In this case, to generate the CDRs, UM needs to read the CDR, and also need to calculate stats based on the period of time, type of call, dialplan, gateway, etc.
Call Stats are generated once per day and can be filtered by month or day for past 90 days.
More info on Call Statistics and individual call logs can be found here.