I am not an expert like Thurask or Conite on all the variants and patches, so I have nothing to offer you about the cause of the delay. Also, there's ambiguity in the language of the Enterprise Recommended program that says phones must be offered unlocked to qualify, but it doesn't clarify if the update policy only applies to unlocked phones.
In any case, I'm not here to defend BlackBerry Mobile or anyone else. I bought my phone from AT&T because I thought there was a risk BBMo might not succeed and wanted a carrier support guarantee if I had a problen.
Posted with my trusty Z10