Yep, hot deploy is handled by the portal and you'll have to hook your way into it.
But the question is how catching the hot deploy helps you? From the portlet's perspective, the code is being overlayed by a new set of code. There's not really much that a user and/or portlet would need to do in the event this is happening... You (the admin) control when the deployment is going to occur, so why does the portlet need to be involved?
Hot deploy is not much different than a regular deployment, except that hot deploy monitors the deploy directory and invokes the process the 'cold' deploy uses upon portal startup; I don't know if you need to distinguish between the two or not.
Finally, it is also possible to manually deploy portlets (by dropping the war in the webapps folder of tomcat or using the admin console of the container). In some cases the manual deployment may be picked up right away, in other cases it won't get picked up until Liferay is restarted, again this would be something to consider.
