The 500 was subsidised from deregulation with Keighley's 1 and Firsts 2-3 buses on certain days of the week. When Metro tendered it as an hourly daily service, dropping the Hebden Bridge to Todmorden section, Keighley won easily as they could simply extend their largely commercial 663, requiring only 1 additional bus whereas First would need 2 to run it.
The B3 is no longer noted as receiving a subsidy.
http://www.wymetro.com/uploadedFile...ravel/maps_and_guides/Bradford_Freq_Panel.pdf
I hardly think a list of Bradford bus services is a definitive source, especially when the Calderdale equivalent lists the B3 as being a Metro subsidised service! Given that the service still received a six figure subsidy in 2014, I doubt very much that it has totally disappeared yet, although as you suggest the subsidy only applies Oxenhope to Hebden Bridge.