it depends what you mean by alerts?!
jBPM has a concept of event listeners that could be used for some sort of alerting, but it is up to you as developer to include it in your process definition.
You could take a look at user guide, section that covers event listeners for more details.
In addition, for human tasks jBPM provides two other capabilities:
- notification - sends an email (by default) when task is assigned to a given user
- reminder - sends an email (by default) based on time expiration events to a user assigned to a task
Types of alerts can be freely coded since all event listeners are java.