Mobile network operators (MNOs) concurrently use different generations of wireless technologies. The base stations (BSs) of different technology generations are co-located in order to decrease operational costs. Furthermore, the MNOs cooperate in order to co-site their base stations. Such an urban site includes more than 25 actively radiating antennas on average with different frequencies and modulations. Electromagnetic radiation (EMR) measurements performed in such an environment may have reduced accuracy. In this paper, the authors propose a new approach for the measurement of EMR in multiple mobile technology interwoven urban BS sites, where more than one operator exists. The maintenance activities are also investigated with their frequency of occurrence and their duration for EMR exposure assessment and the statistics are reported for the first time in academia. On sampling the signal strength and radiation in different positions for the tested urban sites, electrical field strengths as high as 90 V/m were observed. The results are classified according to frequency bands and possible technologies. The probable bioelectromagnetic effects of such EMR exposure on maintenance workers are discussed with the provision of statistical data of co-located BSs and their maintenance activities. A new occupational EMR exposure risk assessment approach is proposed by taking into consideration the massive multiinput multioutput (MIMO) antenna technology.