[css3-fonts] @font-face matching and font-style descriptor

Following feedback on one of our public testcases [1], I contacted John
to clarify some of his comments. While we have resolved the issue with #test3
in the testcase [2] and John will soon edit the spec to clarify it, I
am still unclear about the disagreement over #test1 and #test2 which I reduced
to the attached testcase.

Given the following CSS:

            @font-face
            {
                font-family: MyTestFont;
                src: local(Arial);
                font-style: italic;
            }
            #test {
                font-family: MyTestFont;
                font-style: italic;
            }     

...does #test render as italic or not ?

Firefox and Opera say no. WebKit and IE9 say yes.
So Firefox/Opera only use the font-style descriptor for font matching. 
IE9 and WebKit use it for both matching and styling.

The first question is: what does the spec say ? Is there prose that unambiguously 
states who is right ?

>From John's comment #2 in bugzilla[1], it seems Firefox and Opera reflect the
spec's intent.

If that is the case my next question is: is this really what authors want ? It seems 
the only way they will get italics in this case is by using a font file that only 
contains an italic face. Thus this behavior seems to imply that either 1) making 
font-style:italic match a custom normal face is a more common scenario than choosing 
a different italic face as the italic style for a family or 2) that web fonts will 
generally segregate normal and italic faces for this purpose. 

So while Firefox and Opera may be valid per the intent of the spec today, it's not at all 
what I expected and I suspect a number of authors will be surprised to get a normal face in 
this case.

Thoughts ?

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=589654
[2] http://samples.msdn.microsoft.com/ietestcenter/css3/fonts/font-style-descriptor.htm