Run a 22/4 from panel in house to hub in garage. Home run all runs in garage to said hub. Add keypads, zone expanders as needed, etc. Ernie is right that a toner wand emits a lot of noise when near a keybus line but we have ran them together with other wires in past without noticed effects.

For the partition, I would suggest putting it on its own. You can still access it from the house keypads by holding the # key down for 5 seconds and then select the partition you would like to control. It helps to rename them because by default partition 1 is "System" and partition 2 is "partition 2" which usually doesn't make sense to the end user.