T-Mobile confirmed with me that no amount of programming on my part could violate the TOS etc .. so they verified that it was "bricked" and i could not access the bootloader or recovery screens .. i paid a shipping charge and am now happily cruising on my replacement phone
now i say programming .. that's software .. if you physically damage the phone (ie: open it and mess with the hardware) they won't replace it
I wish I could say I got the same response. I just called up and told them the honest truth and was told that installing hacked ROMs is a violation of warranty and would not be covered (as expected).
For future reference, T-Mobile "doesn't recommend *routing* the T-Mobile G1 because [they] have the official version of Cupcake coming out, which has been tested - whereas third-party releases were written by other people and are different untested versions of the software."
After that I asked for Tier II tech support to see what they would say about not being able to get into recovery mode or the bootloader, and the customer service rep who answered the phone told me that she, as a G1 specialist, was the highest authority on G1s at T-Mobile. I called back and went straight to Blackberry/PDA support (higher level techs) and after doing whatever he could to help, the guy told me there was nothing T-Mobile would do for me.
BTW - I was bricked installing JF 1.43 *after* moving to Haykuro's latest SPL. Apparently, it JF 1.43 downgrades the radio (I'm guessing). Not the way to get Alt+B option back for recovery, regardless. No recovery or bootloader - just the G1 screen.