The problem I blogged about in this post - that no two aggregated thefts are alike and therefore it might be difficult to determine whether different patterns of aggregation are based on the facts of the case or inconsistent application of policy - is far less of a problem in cases where the state seeks to upward depart.
The range of non-trivial reasons to upward depart is much more narrow. If the state seeks to upward depart based on "persistent involvement based on same or similar criminal activity," it is not difficult to compare your client's criminal history with those defendants with worse criminal histories against whom the state did not seek to depart upwardly. Even easier, "on supervision." I'm sure there are many defendants who were on some sort of supervised release against whom the state did not give notice, which means the state needs to articulate some other policy basis for the inconsistent application or it's an equal privileges violation. More amorphous departure factors, such as "harm substantially greater than typical," are easier to place on a spectrum of similar crimes and similar harms - for the purposes of comparison - than aggregation of thefts.
The first step is to get a copy of the DA's policy on upward departure. You really should start thinking about getting it the moment you get a notice from the DA's office, just in case there's a fight over obtaining the policy. You do not want to be fighting over the existence of a policy in the last day or two before getting ready for trial. And it may turn out to be quite easy. Call up the prosecutor and ask. Or, if necessary, get permission for a pre-trial subpoena. Or use a freedom of information request. The bottom line is, just get it. And if you are stymied every step of the way, just file the equal privileges challenge and subpoena the DA to the hearing. If you've got a big enough office where you receive upward departure notices routinely, eventually even the most obstinant DA will just turn over the policy rather than be subjected to a variety of cross-examinations. But I have confidence that most offices will be reasonable and would be happy to provide any written policy - or an affidavit describing the unwritten policy - if approached professionally.
Once you have that policy, then you need to find cases of inconsistent application. How you do this will depend on a number of factors - not least of which is the size of the office in which you work - but other defense lawyers have an incentive to cooperate and share the notices they've received (or haven't received) in similar (though preferably closed) cases.
Of course, if the state isn't threatening any of your clients with upward departures, then you're quite justified in keeping veddy, veddy quiet.