while there is not much info on the G45 yet all indications are that it should work with the G17 mags but I would contact Glock and ask to be sure U.S. Headquarters
GLOCK, Inc.
6000 Highlands Parkway SE
Smyrna, GA 30082
USA
Phone: 770-432-1202
FAX: 770-433-8719

G45 mags are Gen 5 G17 mags, be aware Gen 5 G17 mags will not fit in a G19X but will fit the G45 {due to the extended lip on the front of the G19X magazine well blocking the front of the Gen 5 magazine floor plate}. Gen 5 mags are the same as gen 4 except for the followers{orange} and mag floor plates {stick out more in front than Gen 4 & 3 floor plates} mag numbers on both are 1587-01.

The G45 is just the black version of the G19X, so yes it should accommodate for the Glock 17 mags considering the 19x is a 19 slide with a 17 frame. And the only reason why it is called Glock 45 instead of Glock 19X is because this is their 45th patent. And Glock is known for naming their firearms after the number of the patent.