It certainly isn't an Intel 8214, I think I have some in stock here. The Intel is branded with the 'i' logo and the 8214 was an interrupt prioritizer for the 8080 MCU family. I have some strange things in my storage boxes here!
Almost certainly the 'BTT' is a house code system. When a custom device is made, the number on it is decided by the designer and it rarely if ever follows the coding the same manufacturer uses for generic devices. Being of 1979 date code it could be a small scale memory but unlikely to be more than around 2K capacity and I would think it unlikely to be a complex device. There were no gate programmable devices in that era and the standard MCU was the 8080 and Z80.
There was no "British Telephone and Telegraph" company, at least one involved in electronics, they used the name "Standard Telephones and Cables" or STC but if I remember, their custom devices used STT prefixes.
Brian.