Myself owning a ps2 with bb navi can tell you this will not work. #1 in order to log the ps2 into the BB navi servers it checks for a Jap Ps2 via the cd/dvd rom chip. #2 I am pretty sure the BB Navi servers have been down for over a year, will check if you want me to. #3 BB Navi itself is only compatible with the HDD so you would pretty much have to re-write it to work with a USB device.
Essentially if you really want BB Navi to work get a jap ps2, the HDD (legit sony one) and I can send you a copy of the discs.
JAP 60GB PS3 (release date)
37000 L V7 Ocean Blue Matrix Infinity BB Navi (.32)
30001-R V4R Magic ICE 91f3+ PS2 Linux (2.4.1)
10000 V0 No Mod, PSP-1000 1.0 FW 100K release model
PS2 Linux Kit (BB Navigator Installed)
Scph-5501 Stealth, All Sega Systems
Cube with Save, Xbox 1.0 Modded