The only way it would increase bandwidth is if it evades artificial throttles. Having two connections to the same (neighborhood) pipe seems useless.
Well obviously. They give you a specific bandwidth for your house, you can buy more or less bandwidth if you want.
> Having two connections to the same (neighborhood) pipe seems useless.
The neighborhood pipe can probably do 100 to 1000 times the bandwidth to each individual house. So how is that useless?
Plus with xfinitywifi they allocate double bandwidth to the house, so the wifi bandwidth doesn't slow down the purchased bandwidth. (The cable modem can easily handle 10 times the bandwidth typically allocated to it.)
UPC only makes a small amount of bandwidth available on the 'Wi Free' (UPC's version of Xfinity) network, seems to be about 2.5mbps down and 0.5mbps up. In my country (Ireland), the minimum package you need to get 'Wi-Free' is 120mbps down, so It's not really worth the effort for an extra 1% bandwidth.
Possibility two: placebo effect.