Version: 1.0.5 (but have seen in all tried thus far)
Whenever an mdAutocomplete is on a regular page, the scroll mask gets applied like it does with mdSelect, and keeps the page from displacing the suggestion container by removing the ability to scroll the page while it is open. However, whenever you put the autocomplete in an mdDialog, the scrollmask is not applied and scrolling in the dialog will displace the mdAutoComplete's container of suggestions.
CodePen: http://codepen.io/anon/pen/xVbyZO
This issue is closed as part of our 鈥楽urge Focus on Material 2' efforts.
For details, see our forum posting @ http://bit.ly/1UhZyWs.