Calibri is not a standard font and is owned by Microsoft so I would caution against it's use in digital format as a default font for a business other than potentially for some printed works. The Calibri font is packaged with MS Office, so only if your customer is using Office will they have that font. Should the business be using Google Docs or look at it on a phone without the font, they will see their system default. Also, because the Calibri font has licensing restrictions I don't believe you would be able to use it as a webfont on your landing pages either which is probably why Eloqua/Oracle does not allow the font to be used in their system. I am also including a link to Microsoft's legal documentation on the Calibri font for your reference.
I would take this information back to your brand department and ensure they are aware of the legal situation of using this font.
http://www.microsoft.com/typography/fonts/font.aspx?FMID=1914