If you look at radiation emission maps for antenna, this is not true. Signals will radiate evenly unless shaped by the antennas. The antennas shape the radiation to majority front. Looks like a giant infinity symbol, majorly biased to the front. Back lobes, and indeed side lobes, exist and can be used to connect from the backside of an antenna from quite a distance when you have the proper settings for what you are using to connect with. There is no "safe" side of an antenna when it is of sufficient power, just sides that are relatively more or less powerful than the others.

The only safe way to work on cell towers for repair/maintenance is to shut the equipment down. Inconveniencing a few customers is infinitely preferrable to replacing a skilled technician that gets fried by electricity or cooked by the microwaves. Many repairs only take an hour or two. The down time is negligible in the grand scheme of things. Skilled climbers are valued as most people tend to be unreasonably scared of heights thus replacing workers can be difficult. Customers are practically a given when the cell companies are a virtual monopoly, they don't factor into the equation all that much.