I stand corrected: I just checked my shelf and Hellblazer 21-25 has the 'DC Vertigo' logo rather than just 'Vertigo' - its so minor though that you can barely see it and Im cool with them at least keeping the Vertigo logo long after Black Label was around. Vol 1-20 have the old school Vertigo only logo - I bought all those the day they came out.
Hellblazer Vol 25 just came out in the last couple of weeks and it still has the DC Vertigo on there - and all the solicit pictures im seeing of the final Volume 26 have DC Vertigo as well - those can change though of course.