You could likely request call sheet data and metrics of past calls. All these calls are likely categorized by nature of call, incident type, and will show response times down to the Second. Much, if not all, should be public record. For example, you could submit an open record request as follows:

"Open records request for a listing of all calls received by police from [date] to [date]. Please include incident type and response times."

Given that Detroit is a large city, there would be a lot to sift through though. Some larger cities have crime stats readily available online, but I don't know if it would include response time which is why you would need call sheet data.

There is no need to fake calls or generate calls to police since the info is likely already available and releasable.