The timeline control currently restricts the users to select events from only one group. It must allow selection across the groups. It does not make any sense in restricting the user to a group. Also to deselect an event from selected events is not possible and the user has to deselect all the events and start from scratch. This seems to be a bug with this tool.
Keyur, do you have in mind the Timeline view of the scheduler control here? And if so, can you simulate the unwanted behavior on this demo (http://demos.telerik.com/kendo-ui/scheduler/timeline) or by putting together a simple test case at dojo.telerik.com? Thus I'll be able to evaluate your request.