I read somewhere that there is a technical limitation that prevents the 622 from receiving IR for TV2 in dual mode. You see, TV1 and TV2, in dual mode, have to be able to operate completely independantly and simulataneously. An IR receiver can only see and respond to a single recognized command at a time. Since it's possible someone on TV2 and TV1 could simulataneously issue a command to the 622, they have to be on seperate receivers. In this case TV1's receiver is IR and TV2's receiver is UHF (thereby, 2 seperate receivers). If Dish had placed two discrete IR receivers on the 622, then you would probably be able to use two IR remotes set to two different channels to control the TV1 & TV2 independantly in dual mode.
The only way that we'll ever be able to use an IR remote to control TV2 in dual mode is if someone creates and IR to UHF device specifically designed for Dish's dual-tuner receivers. This device would be connected to the port where the UHF remote antenna is normally connected and then either be wired into a home IR distribution system or placed somehwhere that the TV2 remote could have line of site with it.
I really wish a box like this would come out, as I do not like Dish's UHF remote's very much (Despite haveing 3 of them to control my 4 TV2's). I use a pair of Home Theater Master remotes (an MX-700 and URC-200) to control my main (TV1) set from the two rooms it's visible from (living room and kitchen/dining). I would really like to put URC-200's in all of the TV2 locations, but cannot since they cannot transmit Dish's proprietory UHF codes.
I think, if dish made this magic box I speak of, they would sell a decent amount of them and could probably charge a premium for them, as custom installers and system integrators, in particular, would use them extensively (and give Dish an edge on getting their systems in high-end custom installations). Of course, they'd sell quite a few of 'em to hard-corps consumers like us as well.
Another option, that Dish could put in their next 'flagship' receiver, is for them to put a "zone 2/TV2" monoplug input for IR on the back of the receiver for IR input from remote locations. This is what makers of multizone home theater receivers (like my Yamaha DSP-AX1) do.