A FlyerTalk Posting Legend
Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 100,417
When I did a T1 to T2 connection a while back, the bus left from a normal "gate" in T1 so I was airside at that point just like a passenger departing from T1. [I would have gone through the usual T1 connections security check when getting off of the TATL flight.] The bus service was infrequent (and required taking the correct bus that was funded by the airline to which you were connecting) so it required lots and lots of time. Upon arrival at T2, there was a window checking boarding passes again and then a security check before I could get to a T2 lounge (IIRC JAL for a QF flight).
IIRC I first used a DL SC before switching to the other terminal because I remember someone that I'm sure was a lounge dragon telling me to allow time for the T1 bus, which stopped operation fairly early in the evening. However, if you're connecting to a nonSkyTeam carrier, I would expect that you would not be admitted to the SC now. You should check the access rules carefully for your situation and carry a printout if you find something that says you can use the SC in your situation.
BTW there are one or two landside PP lounges in T2, but they're not particularly good--the SCs at NRT are much better. There might also be a lounge in T2 that you can pay to use.