From 5 Noritsu 3411s at different Costcos:
Printing RelCol with a requested color of Lab(70 20 20). It's arbitrary but is the one I used as an example earlier.
This is a list of the printer locations and proof colors generated:
Profile: Costco-CA-Carlsbad-Gls SoftProof Color: 70.1, 20.0, 20.1
Profile: Costco-CA-Danville-Gls SoftProof Color: 70.2, 20.0, 20.1
Profile: Costco-CA-Santa Clarita-Gls SoftProof Color: 70.1, 20.0, 20.0
Profile: Costco-CA-San Diego-Carmel Mtn. Rd-Gls SoftProof Color: 70.1, 20.0, 20.1
Profile: Costco-CA-Sacramento-Expo SoftProof Color: 70.1, 20.1, 20.1
This is a list of the last 4 printers using the Carlsbad printer to show that the printers do have some variation, though fairly small.
Profile: Costco-CA-Danville-Gls Printed on Carlsbad printer - Lab: 71.2, 20.5, 21.1
Profile: Costco-CA-Santa Clarita-Gls Printed on Carlsbad printer - Lab: 72.0, 19.0, 19.3
Profile: Costco-CA-San Diego-Carmel Mtn. Rd-Gls Printed on Carlsbad printer - Lab: 72.9, 20.9, 20.0
Profile: Costco-CA-Sacramento-Expo Printed on Carlsbad printer - Lab: 72.2, 20.6, 20.5
As you can see, the variations between printers make very little difference soft proofing. I would expect more differences using different profiles when soft proofing the entire sRGB aRGB, or ProPhoto gamuts but I would still expect those differences to pale in comparison to the differences between the initial image and the proofed (or printed) image.