Sometime ago I wrote something quick and dirty that does this. It has no UI - you have to edit the values in a the parameters section of the code, near the top:

---

import poser, random

'''
ALL MEASUREMENTS ARE IN INCHES!!!
'''

Parameters

PROP = 'RuntimelibrariespropsVegetationTreesBlossom tree.pp2'
XTRANSNAME = 'xTran'
ZTRANSNAME = 'zTran'
YROTATENAME = 'yRotate'
MAXIMUM_NO_OF_INSTANCES = 30
MIN_X = -500
MAX_X = 500
MIN_Z = -500
MAX_Z = 500
RANDOM_ROTATE = True
MINIMUM_SEPARATION = 100
GIVE_UP_AFTER = 8

scene = poser.Scene()

Initialise variables

count = 0
rangeX = MAX_X - MIN_X
rangeZ = MAX_Z - MIN_Z
done =

print 'Starting prop generation ...'

while count < MAXIMUM_NO_OF_INSTANCES:
    
    # Load the prop
    scene.LoadLibraryProp(PROP)
    prop = scene.CurrentActor()
    print 'nProp #%s loaded' % (count + 1)
    
    # Generate random co-ordinates
    attempt = 0
    give_up = True
    
    while attempt < GIVE_UP_AFTER:
        bx = (random.randint(0, rangeX) + MIN_X)
        bz = (random.randint(0, rangeZ) + MIN_Z)
        x = bx / 103.2
        z = bz / 103.2
        block = (int(bx / MINIMUM_SEPARATION), int(bz / MINIMUM_SEPARATION))
        print 'Attempt %s: x,z = %s,%s, block = %s' % (attempt, bz, bx, block)
        if not done.get(block, None):
            done[block] = prop
            give_up = False
            break
        else:
            attempt += 1
    
    if give_up:
        print 'n--- GIVING UP!! ---'
        break
    
    # Place prop
    prop.SetParameter(XTRANSNAME, x)
    prop.SetParameter(ZTRANSNAME, z)
    print 'Positioned at %s, %s' % (x, z)
    
    # Rotate if requested
    if RANDOM_ROTATE:
        r = random.randint(0, 360)
        prop.SetParameter(YROTATENAME, r)
        print 'Rotated to %s degrees' % r
    
    count += 1

print 'nAnalysis of prop generation:'
for k, v in done.items():
    print 'Block %s : %s' % (k, v.Name())

Free stuff @ https://poser.cobrablade.net/