After investigating a little bit, I found, that there's no easy way to get the list of all installed packages (or maybe I haven't dug deep enough?). If there would be such a way, then I would just iterate over all packages, looking for their workflows having same ID as workflow I am currently running ("workflow.currentWorkflow.id") as I assumed in my first post. But it looks, that to do that I need to register local vCO instance as its own RemoteServer and then I get "RemoteServer.findAllPackages()" method.
That is getting too complicated and time consuming (RemoteServer registration can take minutes).
So I probably will use another approach: in a workflow I'll create an attribute with "Package" type pointing to the package containing this workflow. As I checked, this approach survives "package export/package delete with content/package import" cycle, so after package import attribute still holds proper reference to the package which was just imported.
Can anybody suggest better way to achieve it?