Possibility for external candidates to receive job alerts for reqs that are only posted internally

Summary:

Is it possible for external candidates to receive job alerts for requisitions that are only posted internally?

We are currently building a custom internal career site for our internal candidates that are not yet in the Oracle system. Once they apply to that custom internal career site, they will be treated as external candidates because technically they don't have a candidate profile yet in the system. However, the jobs posted in the custom internal career site are those requisitions that are posted internally.

We understand that when external candidates subscribe to job alerts, they will receive the notification based on the external requisitions that are posted. Our issue is that yes, candidates will be treated as external candidates when they apply from the custom internal career site, but can they be notified too on requisitions that are posted internally?