You have to make assumptions on what the foundation is to give reaction forces. Since you don't have control over the foundation, you should provide some basic vibration information and let the foundation engineer incorporate that into his design.
In the industrial structures industry I work in, one of the biggest gripes we get from clients is excessive vibration of a foundation or structure from a piece of rotating or reciprocating equipment.
It's rare that we get this data, but you could alleviate some of the heat from your company when the client complains about vibration by providing the following to the foundation engineer: operating frequencies, mass, center of mass, center of rotating mass, 3-axis phase angles of the vibrations, and accurately dimensioned bolt hole size and spacing.
As a Value-Added item, you could sell the option of vibration isolators mounted to your machines. The data above is still required, but also include the damping of your isolators.