When an IOrder object is requested, is a reference to the original object returned, or are the IOrder objects constructed on request?

For example, in the following code, suppose orderA and orderB refer to IOrder objects corresponding to (the same one or two different) market orders.

assert(orderA != null && orderB != null);
boolean e1 = orderA == orderB;
boolean e2 = orderA.getId().equals(orderB.getId()));

Is it true that e1==e2, regardless of where and when orderA and orderB were obtained (e.g. from engine.submitOrder, message.getOrder, engine.getOrderById, etc)?

Well, after some testing on the platform the answer seems to be yes.
i.e. IOrder object identity implies order identity.
So it seems to be safe to store IOrder object references and meaningfully compare their identity to other IOrder object references later, (and use them as keys in IdentityHashMaps, etc).
It would be nice to have a guarantee though.

Also can confirm that it appears IOrder objects are unique for a position. For example, store IOrder object on creation of position (ie, engine.submitOrder()), compared the returned IOrder to all related returned IOrder objects (ie IOrders from onMessage, history interface, etc).

The reference is returned.