Hi, John:
There is no official answer, because Canon Inc. won't comment on it. Based on actual product testing, though, both of these lenses are parfocal as long as you start out by focusing sharply at the maximum focal length and then zoom back to a shorter focal length without refocusing. Look at the files on a computer monitor at 100% magnification to verify.
If you autofocus after zooming out, the camera may drive the lens to a slightly different distance. This is possible because depth of field is greater at the shorter focal lengths of the zoom lens, assuming a fixed subject distance. But if the image remains sharp after focusing accurately at maximum focal length and then zooming to minimum focal length without refocusing, the lens is parfocal.
Best Regards,
Chuck Westfall
Director/Media & Customer Relationship
Camera Marketing Group/Canon U.S.A., Inc.