Comment by Sanzig

I don't think they array between different DSN sites (getting the baselines sorted out would be a nightmare), but the DSN can array up to four of the 34 meter beam waveguide antennas co-located at any individual site.

The three sites were originally built with a single 70 meter dish each, which are all still operating today. However, when they expanded the sites, they opted to install at least four 34 meter BWG dishes at each site rather than adding a single 70 meter to each. Four of the 34s arrayed together gives the same gain as a 70, but you have the advantage of being able to split them up to communicate with separate spacecraft that don't need the gain of all four antennas. It gives DSN a lot more operational flexibility.