T-1 repeaters. Phone companies use T-1 circuits to feed multiplexer systems to provide phone service, slow data, etc. Inside those cans will be repeater cards.
The green pedestal is a splice enclosure. Since the cable may be carrying regular phone service (POTS Plain Old Telephone Service, it's a technical term, look it up…), they can splice off just the wire pairs they need for the T-1 repeaters.