signalref is required attribute so it must be given for signal events.

To meet your requirement I would try to use rules that the events are inserted into working memory and then rule is responsible for signaling the process, with some custom event listener to check if process instance has been started and if not do the extra processing of that event.

HTH

so in that case I would create a dedicated project (kjar) that will have rule(s) that will be capable of finding out (by using some sort of service) what to do with an event, shall it be consumed by process or somehow differently processed. When it needs to be consumed by event then you'll need to figure out where is this process as in jbpm 6 there are multiple kjars deployed and thus various processes might be in different deployments. Does that make any sense for your use case?

HTH