A link (A tag) does not respect the "disabled" property as per the HTML spec, so if you have a "disabled" link then your developers have done something special to make it that way. Generally a "disabled" link is either not a link at all (text with styles applied to it such as a blue color and underline) or where the default behavior is overridden via javascript like so:
$('#link').click(function(e){
e.preventDefault();
});
There are a number of other ways to get the effect as well. In order to determine whether a link is disabled, you would first have to determine how your developers actually faked the behavior of the "disabled" property. Based on what you find out, you may be able to determine whether the link is disabled by checking the class or other properties.