That's how I understand it. Every time I call now they check the status of the AMC record. The time is billable if the site does not have SW assurance regardless of certification levels.
All the old systems that were sold prior to the new process and the AMC accounts activated before Jan 1, 2007 have been "Grandfathered" with SW assurance to OCT 1, 2010.
I have a feeling things will be a little chaotic when those systems start to lapse.
Additionally, if the site has lapsed for greater than some unknown number of days (I think about 30-60) then to re-up your service there is a Renewal Fee required as well.
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Occam's Razor - All things being equal, the simplest solution is the right one.