If he can get an agreement with the other owner, not difficult at all anymore. He would be smart to spend some money on visiting his local attorney & accountant, and hiring communications counsel if he doesn't have one.
If both owners have other properties in the same market, then there may need to be an analysis done to determine any possible multiple ownership issues that may develop.
Some Issues:
1. Arriving at reasonable asset valuation of properties (I would assume this would be an exchange of assets between two corporate entities);
2. Tax consequences: Sale of one business and purchase of another may escape, or ameliorate effect of capital gains taxes--that's a question for the accountant;
3. Who gets accounts receivables, adjustment of rental incomes (tower), if there would be any shared property, who gets real estate, etc. All those little details the lawyers love to argue about.