Is a CCleaner app for Windows Phone 7/8 possible?
Probably not as WP uses a completely different storage and logic and Developer SDK. But if enough people want it . . . anything is possible.
Trust me with all the issue Nokia and HTC are having with Windows Phone 8 and their "Others" items in the main storage & the awful microSD handle of the OS, lot of people would be glad to see an app like CCleaner ported to Windows Phone.