I get the same, although I noticed something different in the 'install.inf' files. Looking at the ecodrive installer, you see the following:
[Windows Mobile for Automotive 5.2]
Open1 = \iFiat\EDv_R_C_4_EcoDrive-2020_single-install_F.ARM920.CAB
[Windows Mobile for Automotive 5.3]
Open1 = \iFiat\EDv_R_C_4_EcoDrive-2020_single-install_F.ARM920.CAB
[Lauberhorn 6.0]
Open1 = \iFiat\EDx_R_L_4_EcoDrive-6030_single-install_F.ARM926.CAB
And the B&M 5.6 (and 5.5, actually) updater:
[Windows Mobile for Automotive 5.2]
Open1 = C83R.cab
Open2 = C83S_C1.cab
Open3 = COU.pku
Open4 = DEU.pku
Open5 = C83E_C1.cab
[Windows Mobile for Automotive 5.3]
Open1 = C83R.cab
Open2 = C83S_C1.cab
Open3 = COU.pku
Open4 = DEU.pku
Open5 = C83E_C1.cab
So I thought I'd try something, and created a file containing the following:
[Windows Mobile for Automotive 5.2]
Open1 = C83R.cab
Open2 = C83S_C1.cab
Open3 = COU.pku
Open4 = DEU.pku
Open5 = C83E_C1.cab
[Windows Mobile for Automotive 5.3]
Open1 = C83R.cab
Open2 = C83S_C1.cab
Open3 = COU.pku
Open4 = DEU.pku
Open5 = C83E_C1.cab
[Lauberhorn 6.0]
Open1 = C83R.cab
Open2 = C83S_C1.cab
Open3 = COU.pku
Open4 = DEU.pku
Open5 = C83E_C1.cab
And I get it at least doing an 'Updating...' and the woman says so, but then it fails with USB ERROR 20.
I suspect the B&M 5.6 update released isn't actually for later cars with the Lauberhorn convergence unit (signified by the B&M logo next to the USB slot rather than a windows symbol, and the 3.5mm Aux input jack).