It seems that other bridges have also been given this name - see Kennington Railway Bridge
and also the lovely bridge by the Oxford Canal, Isis Lock.
1962: Isis Bridge carries the Oxford Ring Road.
The next ring road bridge upstream is called "Thames Bridge" - don't ask ...
2003: Isis Bridge required a full wet and dry blast and coating system to the 5,000m³ of steelwork. The bridge was also strengthened.
Isis Bridge, 2004