I wonder if they are referring to a peering Internet exchange point (IXP) when they say metro. Basically a building where networks converge and ISPs connect to each other.
yes, though "metro" is a better way to define it since many IXes are geographically distributed throughout their city. For example DE-CIX in frankfurt is in many different datacenters, with their core switches connected by DE-CIX controlled dark fiber. AMS-IX in amsterdam is in many facilities in the same metro area, all the same L2 peering fabric. The SIX in Seattle is in three facilities in the same metro and several local ISPs have built their own extensions of it to Vancouver BC.
A metro in Google-speak generally refers to all of the peering locations in a given city or metro area, not specifically a single IXP.
For example, if you look at the PeeringDB entry for AS15169 (https://www.peeringdb.com/asn/15169), for the London "metro" there's public peering available on LINX at 3 different POPs, and private peering available at Digital Realty, 3 different Equinix POPs, and 2 Telehouse POPs.
