A great many model railroad products are not specific to a single scale, and can be used with any scale. Certainly tools, adhesives, electronics, control, paint and other products can be used with any scale.
Even some products that may seem to be scale specific can be used with other than the stated scale. For example, consider a tree that is 10' high in O Gauge. That same tree would be 20' high on an HO scale layout, and 40' high on a N Scale layout. Buildings of a smaller scale can be used in the background of a layout to increase the impression of distance.
Another example is electronics. DCC manufactures list their decoders as Z scale, N scale, HO scale, etc., but this is purely an indication as to the decoder size. An Z scale decoder can power an HO scale locomotive providing its current rating is sufficient to power the larger locomotive's motor.
The railroad modeler has a great deal of flexibility to use products of different scales to achieve his desired result. Tom's Train Station can help the modeler select the appropriate products to achieve this result.