I found an answer to a similar question on Creative Cow, in case anyone is interested:
Premiere Pro's SDK doesn't allow plugins to control the program - for instance, you cannot use a plugin to create markers or move clips in your timeline. Plugins are limited to affecting the video signal.
So it would appear it's not possible.
If only Adobe would develop Premiere Pro Extendscript support to the level enjoyed by After Effects...
The following works in ExtendScript Toolkit, and PPro CC 2014.
var active_seq = app.project.activeSequence;
if (active_seq != null)
alert("Active sequence = " + active_seq.name);
var new_seq = active_seq.clone();
var test_seq = app.project.activeSequence;
if (test_seq != null)
alert("Active sequence is now " + test_seq.name);