The city combos are in the code release read me file. The shot multipler is now lit after collecting both the KISS and the ARMY hurry ups, I believe on the same ball.
Info from the read me below
Now shot multipliers are available/lit by collecting a set of HurryUps (KISS and
ARMY). Previously they were lit by completing a mode.
The 15 Unique City Combos are:
1) Chicago: Left Ramp -> Right Ramp
2) Pittsburg: Right Ramp -> Left Ramp
3) Seattle: Left Orbit -> Left Scoop
4) Portland: Left Orbit -> Starchild Lane
5) Los Angeles: Right Ramp -> Left Ramp -> Demon
6) Houston: Right Ramp -> Left Ramp -> Right Orbit
7) New Orleans: Left Ramp -> Right Ramp -> Left Orbit
Atlanta: Left Ramp -> Right Ramp -> Left Scoop
9) Orlando: Left Ramp -> Right Ramp -> Starchild Lane
10) Mexico City: Left Ramp -> Right Ramp -> Left Orbit -> Left Scoop
11) Tokyo: Left Ramp -> Right Ramp -> Left Orbit -> Starchild Lane
12) London: Left Ramp -> Right Ramp -> Left Ramp -> Right Ramp
13) New York: Right Ramp -> Left Ramp -> Right Ramp -> Left Ramp
14) San Francisco: Left Ramp -> Left Ramp -> Left Ramp -> Left Ramp -> Right Orbit
15) Detroit: 5 sets of Left Ramp -> Right Ramp