Again, you are being disingenuous here. The average home has upspeed bandwidth of about 600kbps. 40kbps for a call is 6.66% of your upspeed bandwidth.
Couple things - first, the "average" internet user only uses the internet for sending text emails, browsing web sites and the like. The average user does not send dozens of digital pictures or songs out, so upload speed and usage is totally unimportant.
That being said, you would presume that someone voluntarily doing something like this to help himself and his neighbors probably has higher than "average" internet service, since average internet service includes a ton of 768 DSL users. There are plenty of FIOS and cable connections out there that have 10x the upload bandwidth and would never notice a couple hundred KBps going out.
10 calls would be almost 70% of your Internet bandwidth.
In your average case, yes. But not on my network, and I imagine not on any of the other readers of this thread.
This also assumes no actual usage by these users for anything other than phone calls. Browsing, etc, will potentially use more bandwidth than a phone call.
Is there a reason why the microcell could not have it's upstream bandwidth use capped so as not to interfere with the owner's internet service? No.