http://jsfiddle.net/upgrmrL3/1/

When clicking the disable button all options get disabled. When clicking "enable" the options in the select2 dropdown still appear as disabled.

Sometimes the disable attribute is not respected either: by clicking disable the options in the dropdown won't get disabled.

The screenshots were taken on the same fiddle, with some cache clearing and refreshes between them.
Testing was done on Firefox 37.0.2 on Mac OS