Not sure if this is even possible to do with HAL...  For example, my iPod as two partitions on it.  'sda1' has no filesystem; it's just the binary firmware image.  'sda2' has a vfat FS on it and is mountable.  However, since normal USB flash disks use 'sda1', I have a /etc/fstab entry for it, and it shows up in the removable volume list.

HAL says this of the device (22 is sda1, 23 is sda2, and 24 appears to be some virtual device describing that it's an audio player):

22: udi = '/org/freedesktop/Hal/devices/volume_part1_size_34099200'
  info.udi = '/org/freedesktop/Hal/devices/volume_part1_size_34099200'  (string)  volume.partition.msdos_part_table_type = 0  (0x0)  (int)
  info.product = 'Volume'  (string)
  volume.size = 34099200  (0x2085000)  (uint64)
  volume.num_blocks = 66600  (0x10428)  (int)
  volume.block_size = 512  (0x200)  (int)
  volume.partition.number = 1  (0x1)  (int)
  info.capabilities = { 'volume', 'block' } (string list)
  info.category = 'volume'  (string)
  volume.is_partition = true  (bool)
  volume.is_disc = false  (bool)
  volume.is_mounted = false  (bool)
  volume.mount_point = ''  (string)
  volume.label = ''  (string)
  volume.uuid = ''  (string)
  volume.fsversion = ''  (string)
  volume.fsusage = ''  (string)
  volume.fstype = ''  (string)
  block.storage_device = '/org/freedesktop/Hal/devices/storage_model_iPod'  (string)
  block.is_volume = true  (bool)
  block.minor = 1  (0x1)  (int)
  block.major = 8  (0x8)  (int)
  block.device = '/dev/sda1'  (string)
  linux.hotplug_type = 3  (0x3)  (int)
  info.parent = '/org/freedesktop/Hal/devices/storage_model_iPod'  (string)
  linux.sysfs_path_device = '/sys/block/sda/sda1'  (string)
  linux.sysfs_path = '/sys/block/sda/sda1'  (string)

23: udi = '/org/freedesktop/Hal/devices/volume_uuid_4386_2443'
  volume.policy.desired_mount_point = 'ipod'  (string)
  volume.policy.mount_filesystem = 'vfat'  (string)
  volume.policy.should_mount = true  (bool)
  info.udi = '/org/freedesktop/Hal/devices/volume_uuid_4386_2443'  (string)
  volume.partition.msdos_part_table_type = 11  (0xb)  (int)
  info.product = 'iPod'  (string)
  volume.size = 4061637632  (0xf217ac00)  (uint64)
  volume.num_blocks = 7932886  (0x790bd6)  (int)
  volume.block_size = 512  (0x200)  (int)
  volume.partition.number = 2  (0x2)  (int)
  info.capabilities = { 'volume', 'block' } (string list)
  info.category = 'volume'  (string)
  volume.is_partition = true  (bool)
  volume.is_disc = false  (bool)
  volume.is_mounted = false  (bool)
  volume.mount_point = ''  (string)
  volume.label = 'iPod'  (string)
  volume.uuid = '4386-2443'  (string)
  volume.fsversion = 'FAT32'  (string)
  volume.fsusage = 'filesystem'  (string)
  volume.fstype = 'vfat'  (string)
  block.storage_device = '/org/freedesktop/Hal/devices/storage_model_iPod'  (string)
  block.is_volume = true  (bool)
  block.minor = 2  (0x2)  (int)
  block.major = 8  (0x8)  (int)
  block.device = '/dev/ipod'  (string)
  linux.hotplug_type = 3  (0x3)  (int)
  info.parent = '/org/freedesktop/Hal/devices/storage_model_iPod'  (string)
  linux.sysfs_path_device = '/sys/block/sda/sda2'  (string)
  linux.sysfs_path = '/sys/block/sda/sda2'  (string)

24: udi = '/org/freedesktop/Hal/devices/storage_model_iPod'
  info.addons = { 'hald-addon-storage' } (string list)
  storage.policy.should_mount = true  (bool)
  portable_audio_player.output_formats = { 'audio/mpeg', 'audio/aac' } (string list)
  portable_audio_player.storage_device = '/org/freedesktop/Hal/devices/storage_model_iPod'  (string)
  portable_audio_player.type = 'ipod'  (string)
  portable_audio_player.access_method = 'storage'  (string)
  block.storage_device = '/org/freedesktop/Hal/devices/storage_model_iPod'  (string)
  info.udi = '/org/freedesktop/Hal/devices/storage_model_iPod'  (string)
  storage.requires_eject = true  (bool)
  storage.hotpluggable = true  (bool)
  info.capabilities = { 'storage', 'block', 'portable_audio_player' } (string list)
  info.category = 'storage'  (string)
  info.product = 'iPod'  (string)
  info.vendor = 'Apple'  (string)
  storage.removable = true  (bool)
  storage.physical_device = '/org/freedesktop/Hal/devices/usb_device_5ac_1205_000000D2AD77_if0'  (string)
  storage.lun = 0  (0x0)  (int)
  storage.drive_type = 'disk'  (string)
  storage.vendor = 'Apple'  (string)
  storage.model = 'iPod'  (string)
  storage.automount_enabled_hint = true  (bool)
  storage.media_check_enabled = true  (bool)
  storage.no_partitions_hint = false  (bool)
  storage.bus = 'usb'  (string)
  block.is_volume = false  (bool)
  block.minor = 0  (0x0)  (int)
  block.major = 8  (0x8)  (int)
  block.device = '/dev/sda'  (string)
  linux.hotplug_type = 3  (0x3)  (int)
  info.parent = '/org/freedesktop/Hal/devices/usb_device_5ac_1205_000000D2AD77_if0_scsi_host_scsi_device_lun0'  (string)
  linux.sysfs_path_device = '/sys/block/sda'  (string)
  linux.sysfs_path = '/sys/block/sda'  (string)