There is not a standard report in UCCX that shows the number of calls transfered to voicemail from a CSQ. However there are a couple of ways to get at the number.

The CSQ Activity report shows the number of calls dequeued by CSQ. If you dequeue a call before sending it to voice mail you could infer the # of calls sent to voicemail by looking at the # of calls dequeued field.

See the CRS Historical Reports Users Guide for Details:

http://www.cisco.com/application/pdf/en/us/guest/products/ps6488/c1626/ccmigration_09186a00804a2a20.pdf

Otherwise if you know the pilot number for vociemail or how calls are transfered to voicemail you could modify an existing or build a custom report.

CRS Custom Report & Developers Guide can be found at:

http://www.cisco.com/application/pdf/en/us/guest/products/ps6488/c1671/ccmigration_09186a00804a2a4a.pdf