Affiliated Service Group A-Org Test - FSO Corporation Exception

For the A-org test, if the purported FSO is an LLC that has elected to be taxed as a corporation and that is not a professional service corporation (or a professional service LLC), would it fail to be an FSO as a "corporation" that is not a professional service corporation since it is being treated as a corporation for tax purposes?  Or would it have to actually be incorporated under state law (and not just treated as a corporation for tax purposes) to be considered a corporation for purposes of this rule?   

Not sure there is a completely clear answer, since there are no final regulations on point, but if you take the position that this is not an ASG, I think the Service would be hard-pressed to show you were wrong. First, 414(m)(2)(A), which was enacted long ago before LLC's were popular (or maybe even existing as a form or organization in most states) refers only to partnerships and corporations, and you're good on both of those, i.e. you are not a partnership (and have not elected to be taxed as a partnership), and if they want to say you're a corporation, you're good there as well because not a professional service corp (the reg is only proposed, of course, but I believe you have reliance as your question implies). You can also argue that the check the box reg (Reg § 301.7701-3(a)) says you're a corporation for all federal tax purposes, and 414(m)(2)(A) is a federal tax rule.