That was a little side-butterfly which at the time I liked, but became an unpredictable pain the more I thought about it as I rolled through the chapters. If firewire is widespread, and everyone plugs in for power (like we do now with USB), and network is available, does WiFi become as ubiquitous? 3G/4G/5G networks? No idea.
But if Firewire is in the mobile phones for charging on trains, it'll be the same in the homes (firewire plugs, maybe with integrated ethernet by powerline?) and on planes (knock on effect of earlier internet onboard if you don't need to use wireless communications to your device?). Probably should have left it as USB and stuck to trains, but I'm also a technology guy and didn't really think that through!
Same for low powered tablets, laptops, etc etc; all will have firewire on for charging and network.