Sorry for late response.
If you can get I140 to specify CP and get employment letter as I described above, you don\'t need employer\'s cooperation. Of course, it will be better if they know about it.
It also depends on your employer. Some (all the ones I know) employers know nothing about the process. Its their stupid lawyers that set up the "policy" to get their costs down thereby abandoning their first call to serve you.
It is not your task to teach your employer about immigration procedures. If you can easily get employment letter (which is the major hurdle in front of you) and you can travel for the interview, you can do CP. If your company lawyer insists on doing CP and your employer insists on doing only what the lawyer says and will not give you employment lettet without lawyer\'s consent, you cannot do CP.
If your employer might agree to do what the lawyer says not to, you can do CP.
If you are going through NVC, you probably don\'t need I140 approval notice. It is only "nice to have" in regular NVC processing. For AC I140 you do need it.
See also:
http://www.imminfo.com/imminfoftp/imminfo analysis 2.pdf
In rare case that consulate calls your HR department, they will say you are employed with them. I don\'t see much danger in that. Remeber that in many cases (NOT ALL) the employer is clueless about what\'s going on and therefore nothing bad can happen from that.