Radio Frequency (RF) & Wireless Design

One troublesome manifestation of this is spurious signals generated by Inter-modulation of transmitter carriers on a shared tower structure where some of the tenants of the property have receivers (such as "repeater sites"). It becomes particularly difficult to locate and mitigate the corroded joint or fastener when some of the transmitters are not continuous (remotely keyed, or part of a repeater).

Yes, and this is why regular inspections of such repeater sites is required at minimum on an annual basis. Also most external connections should be sealed against environmental effects for RF connections and bonded areas should also be sealed against weathering as well, especially those can create a common mode path for common mode noise.

One of the ways to mitigate IMD is to use repeater channels that are as wide as possible between each channel frequency. The other preventative measure is the to chose even harmonic frequencies as well.

One of the least common ways is to use very heavy attenuators, which help SNR and CMMR but also limit distance of remote users.

Also with digital modes and digital filtering thru DSP filtering becoming more common, this is another alternative. 

Its a bunch of trade-offs when having multiple repeaters on one tower, but thru careful experimentation and selection, a good balance can be reached.