Integer texture support in Intel HD 4600

I am having a problem allocating 64x64 OpenGL textures of the format ALPHA16I_EXT (internal) / ALPHA_INTEGER_EXT.

GPU caps lists the GL_EXT_texture_integer extension as being available. The driver is 10.18.10.3345 (10-31-2013).

The machine is a Dell with a hybrid NVidia/Intel configuration.

My question is more a driver question than a dev question: should the HD 4600 support this texture format? Is there limited support?

Thanks.