Experimenting with pixi-gl-core in Google Chrome ( 51.0.2704.103 ). It seems that GLTexture.js sets the global FLOATING_POINT_AVAILABLE once the gl.getExtension("OES_texture_float") has been successfully triggered. When using multiple instances of this texture class with multiple gl contexts this means that OES_texture_float is only enabled on the first context.
By the way I couldn't find float texture support in PIXI V4 - is that coming too?