Comcast received an $805,800 grant from the Massachusetts Broadband Institute to build a cable network in Montgomery, MBI announced this week. Town officials and Comcast still need to sign a cable franchise agreement. If that goes as planned, Comcast estimates it could have its cable network up and running by the end of 2018. Comcast has agreed to reach around 96 percent of the town's premises, or 360 homes and businesses. The arrangement was approved by town officials in April.