Energy Star Portfolio Manager

Yes, all BD+C projects are eligible for Option 3 under this credit.

In addition to registering in Portfolio Manager you will need to provide your energy and water data for 5 years.

I am working on a project with a single meter that tracks the usage of not just the LEED project, but for other non-LEED buildings on campus as well. I assume this complies because of this exception:

When whole project meters are cost-prohibitive or physically impractical to install

Owners of LEED project buildings or spaces that do not have meters in place that measure energy and/or water usage for the entire LEED-certified gross floor area are not expected to supply energy and/or water usage data unless such meters are installed. Many commercial interiors projects, higher education campuses, and military bases will fall into this category. In PIf1 in LEED Online v3, the project team will need to detail the reasons why whole project meters are cost-prohibitive or physically impractical to install.

If meters are installed post-certification, the project owner is expected to report data for whatever time is remaining on the 5 year period, which begins at the beginning of typical physical occupancy for design and construction projects and the date certification is awarded for LEED-EB: O&M projects.

But does this qualify for the point?

Sounds like you could meet the MPR. You can't earn the EAc5 point without having the meter and agreeing to provide the data.

We have the meter and will certainly provide the data, but the meter measures more than just the LEED project. Would that suffice?

According to your post above you don't have an acceptable meter. The meter must measure the energy and water use of the project only. The fact that it includes other buildings makes it not acceptable. You can't claim an exception to MPR 6 and also earn the EAc5 point.