- In BPMN, pools identify processes rather than objects or subjects. You cannot split a single task between two pools.
- You also cannot split it between two pool lanes. Actually, lanes have no predefined semantics; they can represent anything you want: companies, people, divisions, etc.
So, I'd propose the following. If you have "Software developer", "Designer", "Product Manager" lanes and want all of them participate in a meeting, add one more lane and name it "All project participants". And put the meeting task there.
I think that this won't violate both syntax and semantics of BPMN.
Although you're using Bonita, I'd advise you to visit http://elearning.bizagi.com for a nice online video course dedicated to BPMN diagrams design. It is based on BizAgi modeler, but 1) this modeler is a freeware and 2) There is One BPMN Standard to rule them all. :)