Wow thats REALLY odd, I've NEVER seen it supported IE in any of the applications where I pair any IOS device it never allows MAP access. I need to go play with this some more, you shouldn't have to use SIRI for them if its true MAP though; good find!
Only thing I can think of is the phone supports it for Email and not Texts or the Texts app doesn't support it, this was a huge issue with CUE and the texts app had to be pulled for '13 and they released the siri app for '14. You guys have it working and pulling messages and replying through the screen without siri OR maybe that was the work around?