Strange practices?

Has anyone ever heard of a multi-homed enterprise not running bgp with either of 2 providers, but instead, each provider statically routes a block to their common customer and also each originates this block in BGP? One of the ISP's in this case owns the block and has even provided a letter of authorization to the other, allowing them to announce it in BGP as well. I had personally never heard of this and am curious if this is a common practice as well as if this would potentially create any problems by 2 Autonomous Systems both originating the same prefix. Thanks -Bill