Great test question.

Let's review 3 points here.

NOTE: Micro-Bulk first showed up in the 2015 Edition of NFPA 99.

Please understand your statement was based,

on the Micro-Bulk System being outdoors.

1) 5.1.3.16.1

Your In-Building Reserve can not be a substitute for the bulk gas reserve supply.

2) 5.1.3.5.14.2

Your In-Building Reserve can be a substitute for the EOSC.

(i.e. you have to have an eosc or a in-building reserve)

Now the last part #3, is clear as mud 

3) 5.1.3.5.13.2 

(Micro-Bulk) The primary & secondary supply shall be in the same enclosure.

    5..1.3.5.13.3 

(Micro-Bulk) With a reserve supply, shall be permitted in the same enclosure, or per per all the requirement of 5.13.5.13.1. & CGA M-1.

You have to read the whole section #5.1.3.5.13 ( 8 times )

To this end - In my opinion. The Micro Bulk Vessel and the Reserve Supply shall be in the same location.