EOP is included with any Exchange Online instance (which is included with O365 Business Premium/ Exchange Online Plan 1 & Plan 2 etc):
You would only require the EOP standalone licenses if you are utilising an On-Prem exchange:
In most cases if a partner asks for an EOP add-on, they are probably referring to ATP, so it would be worthwhile checking this:
*We can only provision ATP licenses if we provision the base mailbox (as ATP is only an add-on). ie we can't provision them as an add-on to a subscription we haven't also provisioned.