Let's try A7 C7 as an example and add in the b9, #9 (thereby dropping the 2) and the #11, so each chord is voiced as root, b9, #9, 3, #11, 5, 6, b7. All of these extensions are commonly used over V7 chords. We get:
A Bb C C# D# E F# G
C Db D# E F# G A Bb
See where I'm going? The scales are...