Yes, and no. :D
The 430EXII has no wireless eTTL master capability, just like your T2i, it cannot be used as a master unit in Canon's "smart" optical wireless system, the way your 430EXII can be used as a slave in that system. However, there is one model of Yongnuo flash that can act as an optical master (YN-568EXII), so if you used that on-camera, you could remotely fire the 430EXII off-camera with all the TTL/HSS/remote control goodies that Canon's optical wireless system gives you. All the Yongnuo models with "EX" in the name can be used as slaves in this optical system.
All of Yongnuo's current models (and a lot of sellers are selling older ones, which adds to the confusion) have the S1 and S2 slave modes. These are 'dumb' optical triggers that will trip the flash from any other flash burst. They can be used even with the built-in flash on P&S cameras. S1 will fire on the first flash burst it sees, S2 will fire the flash on the second flash burst it sees (i.e., can ignore an eTTL "preburst"). With the T2i alone, you can ONLY use the S2 mode, since your camera's pop-up flash cannot be put into manual mode. With the 430EXII on-camera, in M mode, you can use S1.
Your main problem, here, is that optical slaving has limitations. The sensor on the flash has to "see" the mastering burst in order to trigger the flash. This means you can't have anything solid blocking "line-of-sight" between the flash and the burst that will trigger it. And if you try to use wireless flash outside in bright sunlight, it becomes more difficult for the sensor to "see" the mastering burst, because it's relatively fainter and there are no bounce surfaces around to reflect the master burst to the sensor. This is why radio triggers are good. But as you've probably found with your current radio triggers, they only convey the "fire" signal and nothing else. No eTTL, no HSS, no remote power control.
Your easiest path would simply be to get another trigger in your current system, and add the Yongnuo flash to it. Or, to go manual-only, and get a YN-560IV and YN-560TX, and then add an RF-603II or RF-605 trigger to the 430EXII.
Yongnuo also makes TTL-capable triggers--the YN-622C and YN-622C-TX (there are similar TTL-capable triggers from Phottix and Pixel). This system can communicate everything Canon's wireless system does (and a little bit more) between eTTL-capable flashes. Yongnuo models with names that do not end in 0 are typically eTTL capable (I think the YN-500EX may be the only exception to this). This can be very convenient.
A third (but most-expensive) option to go with Yongnuo would be to go to their clones of Canon's new "RT" system. A YN-600EX-RT is the Yongnuo clone of the Canon 600EX-RT, and you could integrate your 430EXII into the RT system with the YN-E3-RX receiver. The main advantage here is that the receiver is built into the flash, and interoperability with Canon's own RT gear.
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