We are all on one ticket (Star Alliance Award Business Class) from TLV-(TK)-IST-(TK)-DOH-(QR)-IAH-(UA)-YVR.
So what I am hearing is that BP's might be an issue (ie. At Check in with TK, we will receive our 1st two BP's. Upon arrivial at Doha, we will have to obtain our QR (and maybe our UA) BP, which we should be able to do airside at Transfer desk), and if no UA BP issued at this point, then we collect in IAH. Otherwise, interlining of luggage bagtags is possible all the way through, except we have to clear US customs in IAH as per usual collect bags off carousel then re-deposit at baggage re-check. I hope I got this right!