Can own Azure premium licenses be used for MFA in B2B sharepoint

[dgoossens]

Hi,
We would like to setup a B2B Sharepoint site to allow safe sharing of documents with another company.
Since we would like to protect the access from the other company with MFA, we'll need to provide an Azure license for them.
The other company however is also using Office365, and probably they already have the required license available in their tenant.
Do we need to buy additional Azure premium licenses for these users, or can they use their own license to access our Sharepoint?
I found this on the internet : "if the guest user already has an AAD P1 license assigned to their identity by their own employer, then it will not even count against the guest license allocation"
But I cannot find any official statement that it would be the case.

[#2]

Hello, AFAIK the inviting organization performs MFA and must make sure that it has sufficient AAD Premium licenses for their B2B users who are using MFA. It used to be the 1:5 ratio (5 guest users) but there's a new billing model you can read about here https://docs.microsoft.com/en-us/azure/active-directory/external-identities/external-identities-pric...

Hope it helps!