Generate Azure Policy Compliance Alerts By Sending Custom Data to Log Analytics - Part 1

That scenario was not specifically tested in this scenario but the only resource that is specific to a subscription is the Event Grid Subscription, which is assigned at the subscription level.  In theory, the Azure Function and Log Analytics workspace could be used if you had access to it but again this was not tested in our scenario.  The Event Grid Subscription will only capture the PolicyInsights data for the subscription it is subscribed to so you would definitely need another Event Grid Subscription for additional subscriptions.

You could certainly test your scenario by creating a new Event Gird Subscription and attempting to send it to the original Azure Function / Log Analytics.  Worst case scenario, standing up another instance of the Azure Function and Log Analytics is not a time consuming effort.