Urmila Singhal has written very detailed and interesting posts on how to interview for a technical program manager role.
Interviewing to become a Program Manager from a different role: Introduction to what are the skills needed to become a Program Manager - http://www.urmilasinghal.com/2012/11/interviewing-to-become-program-manager.html
Is project management like parenting? - Interviewing for a program manager Part 2: What is Project Management, what are the different methodologies of Project Management - http://www.urmilasinghal.com/2012/11/is-project-management-like-parenting.html
Communication with your grandma and the technical architect at the same time - Interviewing for a program manager Part 3: What is communication, its importance. Principles of communication and Different types of communication - http://www.urmilasinghal.com/2012/11/communication-with-your-grandma-and.html
Approaching design questions in an interview - Interviewing for a program manager Part 4: What is design and the types of design questions - http://www.urmilasinghal.com/2012/11/approaching-design-questions-in.html
Abstract Design Questions Approach - Interviewing for a program manager Part 5: Approach to abstract design problems with examples - http://www.urmilasinghal.com/2012/12/abstract-design-questions-approach.html
Architectural and Algorithmic design questions - Interviewing for a program manager Part 6: Example of an architectural and algorithmic design problem with a solution - http://www.urmilasinghal.com/2013/01/architectural-and-algorithmic-design.html