for my DROID 4 phone, after the system upgrade to Ice Cream Sandwich, I can now (under 'wireless & networks) - More - Mobile Networks -
see the options for Network Mode 'Global or LTE/CDMA or GSM/UMTS'.
A) when selecting 'global', the phone does not connect to a roaming partner and when checking 'Network Type and Strengh', reports 'no service'.
B) when selecting "GSM/UMTS" is 'sees' 5 local network provider (t-mobile germany, vodafone germany, o2 service germany, eplus service germany and eplus 3g service germany), but even if directly selecting one of those, the phone only gives an error message in the upper left corner (little yellow triangle), and when looking at this, it sais: "No service - Selected network (Vodafone.de 2G) unavailable"
i have checked with Verizon and the phone is set to global, i.e. global roaming should work.
1 Do you have international data plan? If this is not enabled on your Verizon SIM, then "Global" roaming partners might not be visible.
2 UMTS/GSM setting "sees" local available networks, so you need a LOCAL: SIM card to use these. Which is what you should be doing anyway, go into oone of those carriers outlets and pick one up. Most European local plans are a lot cheaper than US plans and most include tethering at no extra charge if this is of value to you.
This does sound like the Verizon SIM is preventing access (since the networks are visible). So none of the 5 work?
I would ask Verizon if a special SIM activation is needed. On the older (pre-LTE) Androids, you had to have the SIM activated for use on GSM networks. Now of course the SIM has to be activated for use in the US anyway, so maybe not.
As diamap52 says, going with local SIMs is the best approach anyway (unless you really need people to be able to contact you on your US number, and there are services to do this as well with local SIMs), but on other forums people have reported success using the Verizon SIM in Europe. After all, VZ wants you to do this so you can pay them a lot of money!