I read yesterday that more people in India have access to a cell phone than to a toilet or running water. I assume they are very poor since they have to poop outside on the street, but they do have cell phones.
I think it is safe to bet that, among those using public transport, mobile phone ownership will not be higher. Also, of those with a mobile on those buses, mobile phone _usage_, likely, will be higher for the richer ones.
"Access to" and "owning it oneself" are not necessarily equivalent. If a household of seven has a single cell phone, seven people have "access to" a cell phone.
Mobile phones and internet access via mobile phones is a pretty high priority, even if the other items on the list are a toilet, a scooter, or a stove. The rationale is that the phone and internet enables you to earn more and get the other items.
I think it is safe to bet that, among those using public transport, mobile phone ownership will not be higher. Also, of those with a mobile on those buses, mobile phone _usage_, likely, will be higher for the richer ones.