1) WP7 + Windows Mobile is probably still growing in absolute numbers, but just being outpaced by Android and iOS growth
2) These numbers only represent consumer devices, not business; from the comScore report: "Data on mobile phone usage refers to a respondent’s primary mobile phone and does not include data related to a respondent’s secondary device.". In particular, many people have iPhone's for personal use and a BlackBerry/Windows phone for business use.
edit: formatting