I guess you could if you have different contexts (HTTP request cookie space) for each thread, not entirely sure how to do that in Node and probably not the best idea for scalability.
If you create and then use a user with the admin role for API access then it will be able to enumerate all the devices on the system, and can then fire a call against any or all of them inside your timer handler function.
As previously explained device.call() is non-blocking, you give it a callback to invoke when you get the call result from the PBX and just monitor the line status to check the call result. You can therefore fire all your call()s serially and they will execute within milliseconds of each other (for a reasonable number of calls). This should be fine provided you don't murder the PBX by effectively DOSing it with lots of dials at the same time. If you are trying to place a very large number of calls (which will depend on the size of the box) in the same few seconds, then you may want to implement some sort of queue/scheduler to rate limit these.