For the client side having Remote Database API 4.4.x.x or later, and the server side having IMS Database Server 2014-04-04 or later, an experimental batch seismogram retrieval mode is now available that is aimed to greatly speed up opening such remote events from Trace. The new retrieval protocol is also used by an experimental copy of the event copier tool in Trace.
A test using a particularly large (~190 site) event showed a speed-up of well over an order of magnitude. Independent tests of this is encouraged.