They've been bonding many installations for a while now. I do them as a contractor, and my house is bonded too. They used to use a goofy modem in an outdoor rated enclosure, and separate battery box/power supply, and separate wifi "puck".
Thankfully they switched to the 5168 for pair bonding. Cuts down on installation time for sure!
I would love to get higher speeds, except I won't upgrade since it would probably cost more and I spend my money on more important things.
My 5168 is running at 17 Mbps per line (they run them on this profile, never seen anything higher.) I've heard this isn't really accurate, but the GUI says max rate per line is around 45 Mbps (Couldn't imagine almost 90 Mbps on copper!)
I remember one guy telling me about a business product called a Hatteras, that can use up to 6 lines I believe!
Authorized Service Provider (Contractor) for MTS Allstream. Any views expressed are my own.