FogBugz only sends the auto-response (if you have it enabled) for cases which originate from incoming emails. You could try having your app send crash reports as emails to fogbugz, or let your user send an email with the error text, etc. That way your normal mailbox settings would apply (however you wouldn't get the collation of occurrences into one case that BugzScout provides)
We usually try to keep customer communication and bug/feature cases separated (but linked) in order to make sure that each gets the proper attention from the right people. For example, if you emailed a customer in the Bugzscout case, you would dilute the info there and make it less useful for developers. You could also accidentally close the case when you send the reply, or while the case is assigned to a developer, a tech support rep doesn't see that a customer needs a reply. You can read about our email best practices here.