Travel to Oman by Road - Visit Visa (Dubai)

Hi all,
Me and my friend intend to travel to Oman by road. Having UAE Residence Visa, I have travelled to Oman by road crossing the border near Hatta. However my friend does not have any GCC residence Visa but holds Visit Visa issued by Oman. Can my friend travel with me by road from Dubai to Oman or does he have to take a flight to Oman?
Are there any such restrictions for entering OMAN by road for persons holding Omani visit visa?

Rgds
Harshad