sim card "unlocked" question

I have a question about unlocking phones for any carrier. If I wanted to use a phone on another network, like AT&T. I love my t-mobile, but this is for an example. I notice that the htc hero UK version is using ATT's 3g network (I don't know if it is, but this is for the example), so I buy and import that version. Once it's here, I see that another carrier is using it as well. If I install the other carrier's ROM to my phone, will it be locked onto their network or will it still be unlocked? Will I get updates to my phone from the UK version if I'm using it in the states with a different carrier? If I installed the sprint hero rom onto the phone, would it drop the GSM radio drivers and flip out trying to use the sprint/verizon broadcast method (I forgot the acronym)? I can see all sorts of problems with this that could brick my phone, but if I buy a phone from across the pond so I can use the right 3g frequencies, I want to be able to get updates with it as well. Is there a workaround for it or would I be hunting for news tidbits every time there's an update for a downloadable ROM leaked online?

Thanks for your help!
~D

 

So, that's a "no idea" I'll guess. No one knows if updates will get pushed when you're overseas? If it's the htc hero, I know phandroid had a European hero at one point. Did you get updates with it in the States?

 

Yes, I knew about that part, but thanks for responding! The big question I'm asking is this:
If I get a GSM phone like the htc hero from the UK for use in the states and I use it on the GSM network that it would work on (I believe that is AT&T for its 3G), when the people in the UK get their update from 1.5 to 2.0, will I get the update? Are they carrier specific or something else? I know that several phones are having the custom interfaces now, so that would mean the updates for them come from somewhere else? Does the phone check the right servers no matter what part of the world you're in, or do they get pushed by carriers?

 

True, unless I find one that does have those bands. Do you know the answer to the question? My original questions were:
If I get a phone from the UK and put it on a compatible GSM network, will it still receive updates OTA or will I have to try to find them? If I have to find them, will a ROM for a phone released in the US work if flashed to a UK phone, or are the GSM frequencies coded into the ROM so as to make it unusable on something made for different GSM bands?
Thanks for your help!

 

cool. I can live with that if the phone still gets the updates. That is what I have been asking about this whole time. I already know about the bands and frequencies. Do the android updates get pushed out even when you're out of the UK or do you have to download them yourself?

 

ah, thank you! That's great news and exactly what I wanted to know! I had thought they were carrier specific since tmo usually pushed out the g1 updates instead of HTC. Awesome! Thanks again!