Unfortunately, there is no model of outlining regions.  The code model and
editor model let you navigate between them readily by getting the text
locations of the start and end of code elements or asking what type or
member contains a textpoint.  I suspect there is no work around for you
task.  You could collapse all outlining, but that would lose the current
function's outlining state.  You could walk the code elements in the file,
move the editor's TextSelection to each one and invoke the expand/collapse
command, but there's no way to inspect the state of outlining (and the
screen would jump around as this macro executed).

I've seen some other requests for modeling outlining and #region sections,
so I'll at least tell the team that owns this stuff that interest in this
area continues to grow.

Bill