... I don't know of any mobile to PC infections yet, but I do know there are lots of smart people out there. It's just a matter of time before someone starts to try and exploit the capabilities of modern mobile devices, especially those with large storage capacities...
One plausible scenario, where an employee's mobile device would unknowingly be used to infect or breach the corporate network, would be something like a file explorer or synching app, something with a trojan that activates special programming when it detects the user has connected to an intranet.
The following examples are not exactly what I've described above, but it shows how even popular and trusted apps can betray our trust.
https://www.techrepublic.com/article/major-vulnerability-found-in-android-es-file-explorer-app/
https://www.technadu.com/adware-doctor-mac-app-store-spyware/40916/
"Do not seek to follow in the footsteps of the wise. Instead, seek what they sought." - Matsuo Basho