It dawned on me as I'm trying to write some code to synch between 2 Processwire sites that it would be handy to be able to access another site's object and data via the Processwire API.
I'm guessing it hasn't been considered so far, most likely because of security concerns?
It appears to me the only way that is currently possible is to have a Single Database, Multi site setup? https://processwire.com/api/modules/multi-site-support/