Override plugin functions in functions.php

by

It is possible to filter the get_bloginfo(), but you’ll have to find a way to fine tune the conditional, because the override is global…

add_filter( 'pre_option_blogname', 'wpse_58030_override_blogname' );

function wpse_58030_override_blogname( $bool )
{
    // If not page with ID == 28, do nothing
    if( !is_page( 28 )  ) 
        return false;
        
    // Change the 'blogname'
    return "Not The Blog Name";
}

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Observation

get_bloginfo() is the same as get_bloginfo('blogname').

If the desired filter was siteurl, the filter would be pre_option_siteurl.