It seems that the default behavior of the control is to set autocomplete="off".  When setting using the .HtmlAttributes method int he MVC wrappers and setting autocomplete to something else this setting is ignored.

I propose that the HtmlAttributes method should adhere to all settings that are passed into it.

Example using the MVC Wrappers:

html.Kendo().MaskedTextBoxFor(e).Mask(mask).HtmlAttributes(new { @class = "form-control", autocomplete = "tel-national" })