Q&A of the Reduction of Lead in Drinking Water FAQ covers the issue of plating:
Section 1417 (d)(1)(B) defines lead free for pipes, fittings or fixtures to mean “not more than a weighted average of 0.25% lead” when used with respect to the wetted surfaces. The statutory provision for calculating lead content (Section 1417(d)(2)) provides that “[t]he lead content of the material used to produce wetted components is used to determine compliance with the lead free definition.” That provision also provides that, for lead content of materials that are provided as a range, the maximum content of the range must be used. The “material used to produce wetted components” includes all of the materials used to produce any component that has a wetted surface. If a coating is applied to a pipe, fitting or fixture, you must calculate the lead content of both the alloy and the coating and use the maximum lead content. If a pipe, fitting or fixture is treated with a lead removal technology, you would need to calculate the lead content of the alloy used to produce the pipe, not just the surface of the pipe, fitting or fixture -- because the alloy is the material used to produce the pipe and the pipe is the wetted component. If the lead content of the material is provided as a range, you would use the maximum lead content.
The FAQ can be found here: http://water.epa.gov/drink/info/lead/upload/epa815s13001.pdf.