Vendors needing Plant built you will usually need a sponsor to get your foot in the door, Crown Castle is that way, as far as having a contractors license, they are not necessary , but helpful, some states the purpose of some contractors getting licensed is for the purpose of pulling thier own permits if it is required by contract.
Contractors that provide turnkey solutions such as engineering, splicing, termination, activation, aerial, underground companies are what a lot of large Telco Cable , Energy etcc...
look for and be prepared to have the assets for bonding large projects, i am sure this thread will continue with other comments.
just my opinion