[Rules] Can non-personnel units dig in?

[plloyd1010]

Where's the bit about Motorcycles not digging in?  16.23 says Cavalry and unarmed transports, though I don't recall ever digging in motorcycles.

There seems to not be. I thought there was something where the rules were talking about motorcycles, but it seems not.

I don't think I have ever dig in motorcycles either. There would have been an opportunity to give treadasaurusrex even more headaches had I dug in some dragoons.