This is a perl script I cooked up to export from a b2evolution version 1.9.3 database to MT/b2import format for the purpose of merging multiple b2evolution installs. It requires both the DBI and HTML::Entities perl modules.

Lazy shortcuts I made:
* It assumes a single author for all the posts: admin ($default_user).
* It assumes all comments without a "comment_author" to be admin ($default_user).
* It only assigns the default category
* It only imports published comments

#!/usr/bin/perl

# steven b. cherry
# this script exports a MT compatible output file

use DBI;
use HTML::Entities;

my $driver      = "mysql";
my $database    = "b2evolution";  # replace with your db name
my $hostname    = "localhost";
my $name        = [mysql name];
my $password    = [secret];

my $default_user = "admin";

my $dsn = "DBI:mysql:database=$database;host=$hostname";

my $dbh = DBI->connect($dsn, $user, $password);

my $query = "SELECT * FROM evo_posts, evo_categories
WHERE evo_categories.cat_ID = evo_posts.post_main_cat_ID ORDER BY post_ID;";

$qth = $dbh->prepare($query);

$qth->execute;

while ( $row = $qth->fetchrow_hashref ) {

        print qq(AUTHOR: $default_user\n);
        print qq(TITLE: $row->{'post_title'}\n);
        print qq(DATE: $row->{'post_datecreated'}\n);
        print qq(PRIMARY CATEGORY: $row->{'cat_name'}\n);
        print qq(STATUS: publish\n);

        # section delimiter
        print "-----\n";

        print qq(BODY:\n);

        print qq($row->{'post_content'}\n);

        print "-----\n";

        ## comments ##
        my $cquery = "SELECT * FROM evo_comments
        WHERE evo_comments.comment_post_ID = $row->{'post_ID'} AND comment_status = 'published' ORDER BY comment_ID;";

        $cqth = $dbh->prepare($cquery);

        $cqth->execute;


        while ( $crow = $cqth->fetchrow_hashref ) {

                print qq(COMMENT:\n);

                if($crow->{'comment_author'}){
                        print qq(AUTHOR: $crow->{'comment_author'}\n);
                }
                else{
                        print qq(AUTHOR: $default_user\n);
                }

                print qq(EMAIL: $crow->{'comment_author_email'}\n) if $crow->{'comment_author_email'};
                print qq(URL: $crow->{'comment_author_url'}\n) if $crow->{'comment_author_url'};
                print qq(IP: $crow->{'comment_author_IP'}\n);
                print qq(DATE: $crow->{'comment_date'}\n);


                $crow->{'comment_content'} = encode_entities($crow->{'post_content'});

                print qq($crow->{'comment_content'});

        }


        print "--------\n";     # entry delimiter

}  ## while


$qth->finish;

I had to use HTML::Entities::encode_entities() on the comments or the import script would fail.

I also think it's worth mentioning that the MT-import utility doesn't exactly conform to the MT spec: http://www.sixapart.com/movabletype/docs/mtimport. I found that "AUTHOR:" must precede "TITLE:" in the export file which isn't covered in the format spec. So this script may or may not allow importing into MT.