As Chase commented, the actual lmodel2() code and the ggplot code you use will be helpful. But here is an example that can point you in the right direction:
dat <- data.frame(a=log10(rnorm(50, 30, 10)), b=log10(rnorm(50, 20, 2))) mod <- lmodel2(a ~ b, data=dat,"interval", "interval", 99)
Full disclosure: I don't know anything about RMA regression, so I just plucked the appropriate slopes and intercepted them and inserted them into geom_abline() , using the sample code from lmodel2 as a guide. The CIs created in this toy example don't seem to make much sense, since I had to force ggplot to zoom out using xlim() and ylim() to see the CI lines (red).
But perhaps this will help you create a working example in ggplot() .
EDIT2: when adding OP code to extract the coefficients, ggplot() would be something like this:
ggplot(dat,aes(x=b,y=a)) + geom_point() + geom_abline(intercept=fit2[1,1],slope=fit2[2,1],colour="blue") + geom_abline(intercept=fit2[1,2],slope=fit2[2,2],colour="red") + geom_abline(intercept=fit2[1,3],slope=fit2[2,3],colour="red")