It depends on what agreement Amex has with your employer. Corporate cards may give ultimate recourse to the employer.
In my case, when the company started the Amex program perhaps 10 years ago I was denied (prior CO with Amex). My manager had to authorize a $4K guarantee and I was held to that limit, after one year the corporate guarantee and the limit went away.
But bad news is, I don't think Amex will report the corporate card. They don't report mine and never have.
Unless you're a sole owner and used your SSN to apply, that's a new one for me that AMEX will HP you. When I got my Corp AMEX some years ago, there was absolutely no pull anywhere.
They don't even report the card on my file since I don't bear the impact. I haven't used it in over 3 years. Instead, I got permission to use my personal Plat AMEX for work purposes, They pay it off in full and I get the points
I got my corporate Amex in 2008. There was no pull on my credit whatsoever, and the do not report that card to my reports. When I got my own personal Amex in December 2011, they backdated it to the 2008 date on the corporate card (upon my request), and show "OK" history on all 3 credit reports going back to 2008.
Starting Score: 660 Jan 2012