Two things, if you want to use a template hook, you eval it this way - you don't use str_replace:
PHP Code:
eval('$template_hook[usercp_navbar_bottom] .= "Your HTML here";');
Second thing, I am pretty sure you will need to take the <if> out of the html you want to add in there because when that is evaled, the if will not be eval. Use the if as the condition to do the eval:
PHP Code:
if($canaddquote)
{
eval('$template_hook[usercp_navbar_bottom] .= "Your HTML here";');
}
It's not clear to me how memberinfo_block_bfc_quote is supposed to tie in here (there is no mention of $block_data[bfc_quote] in your code).