http://www.w3.org/TR/SVG/styling.html suggests not. CSS2's dynamic pseudo-classes :hover, :active and :focus and pseudo-classes :first-child, :visited, :link and :lang ([CSS2], section 5.11). The remaining CSS2 pseudo-classes, including those having to do with generated content ([CSS2], chapter 12), are not part of the SVG language definition. An SVG element gains focus when it is selected. See Text selection.
In SVG 2 ::first-line and ::first-letter will be applying to <text>; the corresponding section in the SVG 2 draft will need to be updated. Given that, does it make sense for them to apply to <foreignObject>, if that has HTML content inside it?
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