Builders can be placed with any meeple in a city or on a road. Builders are special figures, not meeples.
The rules of any expansion are always written as if you were playing with the base game only... So you, as a seasoned player and rules interpreter, must infer -according to HiG's standards- that when the rules say meeple, you must assume any meeple unless stated otherwise or any constraints apply.
Please check this set of extended comments I prepared for the base game when combined with expansions. I will add it the the main Base Game page eventually:
https://wikicarpedia.com/index.php/Base_Game_-_Test#Interactions_with_expansionsOne of the points deals with the meeple denomination.
General notes:
* A meeple is:
- A normal meeple (Base Game)
- An abbot meeple (Basr Game - The Abbot)
- A large meeple (Exp. 1 - Inns & Cathedrals)
- A wagon (Exp. 5 - Abbey & Mayor)
- A mayor (Exp. 5 - Abbey & Mayor)
- A ringmaster (Exp. 10 - Under the Big Top)
- A phantom (The Phantom)
* A special figure is:
- A builder (Exp. 2 - Traders & Builders)
- A pig(Exp. 2 - Traders & Builders)
- A barn (Exp. 5 - Abbey & Mayor)
- A shepherd (Exp. 5 - Hills & Sheep)
- A messenger (Mini #2 - Messages) - on the scoreboard
- A robber (Mini #6 - Robbers) - on the scoreboard
* A neutral figure is:
- The fairy (Exp. 3 - The Princess & the Dragon)
- The dragon (Exp. 3 - The Princess & the Dragon)
- A tower floor (Exp. 4 - The Tower)
- The Count (Exp. 6 - Count, King & Robber)
- A bridge (Exp. 8 - Castles, Bridges & Bazaars)
- The Big Top (Exp. 10 - Under the Big Top)
- The Big Pink Pig (The Wheel of Fortune)
- The special die (Mini #1 - Flier)
- A ferry (Mini #3 - Ferries)
- A gold ingot (Mini #4 - Goldmines)
- The Mage (Mini #5 - Mage & Witch)
- The Witch (Mini #5 - Mage & Witch)
- The teacher (The School)
- The Gingerbread Man (Winter Edition - The Gingerbread Man)
This page may help you solve some issues about do's and don'ts regarding figures:
https://wikicarpedia.com/index.php/Game_Figures